Rotary pump having a casing being formed with a communicating hole communicating a space that is between the side plate and the wall surface of the driving machine

ABSTRACT

It is intended to provide a vacuum pump so that without upsizing the vacuum pump, noise and vibration are reduced, heat dissipation property is secured, and the casing is downsized. Therefore, at least one turning part is provided in an exhausting path formed in a casing body. The casing body is formed of a material whose thermal conductivity is higher than that of a rotor and vanes, and a cylinder part where the vanes slide is press fitted in the casing body.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional Application of U.S. patent applicationSer. No. 14/992,549 filed Jan. 11, 2016, which is a DivisionalApplication of U.S. patent application Ser. No. 13/638,472 filed Oct.25, 2012, which is the U.S. National Phase Application of InternationalPatent Application No. PCT/JP2011/058656 filed Mar. 30, 2011, whichclaims priority to Japanese Patent Application No. 2011-028480 filedFeb. 14, 2011, Japanese Patent Application No. 2010-267556 filed Nov.30, 2010, Japanese Patent Application No. 2010-267351 filed Nov. 30,2010, Japanese Patent Application No. 2010-083878 filed Mar. 31, 2010,Japanese Patent Application No. 2010-083843 filed Mar. 31, 2010 andJapanese Patent Application No. 2010-083699 filed Mar. 31, 2010, theentire contents of which are incorporated herein by reference.

FIELD OF INVENTION

The present invention relates to a vacuum pump (compressing device)which includes rotary compressing elements in a casing. Particularly,the present invention relates to a vacuum pump which has a rotor that isattached to the rotary shaft of a vane-type driving machine.

BACKGROUND ART

Generally, a vacuum pump (compressing device) which includes rotarycompressing elements in a casing is known. In this kind of vacuum pumps,a vacuum can be obtained by driving the rotary compressing elements witha driving device such as an electric motor.

A vane-type vacuum pump is known as the compressing device. In this kindof vacuum pumps, a vacuum can be obtained by driving rotary compressingelements with a driving device such as an electric motor.

Generally, it is known that the vacuum pump includes a casing attachedto the wall surface of the driving machine, a rotor which isrotationally driven by the rotary shaft of the driving machine in thecasing, and a plurality of vanes which are extendably accommodated inthe rotor. In this kind of vacuum pumps, a vacuum can be obtained bydriving the rotor and the vanes in the casing with a driving machinesuch as an electric motor.

The vacuum pump is carried, for example, in an engine room of anautomobile and is used to produce a vacuum to operate a brake boostingdevice (for example, refer to a PTL 1).

Further, it is known that a vacuum pump includes a casing attached to adriving machine, a hollow cylinder chamber which is formed in the casingand has openings at the two ends of the casing, a rotor which isprovided at the rotary shaft of the driving machine and which isrotationally driven in the cylinder chamber with the rotary shaft, and apair of side plates which block the openings of the cylinder chamber.This kind of vacuum pump is used to produce a vacuum to operate, forexample, a brake boosting device of an automobile, and the vacuum can beobtained by driving the rotor in the cylinder chamber of the casing withthe driving machine such as an electric motor (for example, refer to aPTL 2).

CITATION LIST Patent Literatures

PTL 1: JP-A-2003-222090

PTL 2: U.S. Pat. No. 6,491,501

SUMMARY OF INVENTION Technical Problem

With the vacuum pump of the PTL 1, by compressing the air which is takenin the casing and exhausting the air from an exhausting port by drivingthe rotary compressing elements, a big noise or vibration are producedwhen the air is exhausted from the exhausting port. In the conventionalconfiguration, in order to reduce the noise or vibration, a silencer isprovided at the exhausting port, and attached to the vehicle through astubborn bracket which is provided with a vibration proof rubber. Thus,there is the first problem that the number of components is increased,and the vacuum pump is upsized.

The invention is made in view of the above circumstances, and the firstobject of the invention is to provide a vacuum pump whose noise andvibration can be reduced without being upsized.

With the vacuum pump of the PTL 1, because the casing temperatureincreases by compressing the air in the casing by driving the rotarycompressing elements, it is desirable to cool the casing (heatradiation). In this case, to secure a big heat radiation area, it isconsidered to form the casing by attaching an attaching base to theelectric pump and to laminate the cylinder body on the attaching base,but in this configuration, there is the second problem that the casingextends in the axial direction of the electric motor, and the vacuumpump is upsized.

The invention is made in view of the above circumstances, and the secondobject of the invention is to provide a vacuum pump so that while heatdissipation property is secured, the casing is downsized.

With the vacuum pump of the PTL 1, by compressing the air which is takenin the casing and exhausting the air by driving the rotary compressingelements, a big noise or vibration are produced when the air isexhausted from the exhausting port. Therefore, in order to reduce thenoise or vibration, a silencer is provided at the exhausting port, andattached to the vehicle through a stubborn bracket which is providedwith a vibration proof rubber. Thus, there is the third problem that thenumber of components is increased and the vacuum pump is upsized.

The invention is made in view of the above circumstances, and the thirdobject of the invention is to provide a compressing device whose noiseand vibration can be reduced without being upsized.

The vane-type compressing device of the PTL 1 has such a structure thatthe vanes fly out due to a centrifugal force with the rotation of therotor, and an underpressure is produced in vane slits which accommodatethe vanes when the vanes fly out, and this underpressure acts as a forceto disturb the flying out of the vanes. In particular, in a layout thatthe vane slits are offset to positions apart from the rotation center ofthe rotor, or when the vanes are made of lightweight carbon, because thecentrifugal force acting on the vanes becomes small, it is very likelyfor the vanes to be influenced by the above underpressure. When awell-known mechanism for helping the flying out of the vanes is used toavoid the influence of this underpressure, there is the fourth problemthat the number of components is increased and the compressing devicebecomes expensive.

The invention is made in view of the above circumstances, and the fourthobject of the invention is to provide a compressing device so that thenumber of components is not increased and the flying out of the vanescan be easy.

With the vacuum pump of the PTL 1, by attaching the casing, whichincludes a hollow cylinder chamber that has openings at the ends, andside plates that block the openings of the cylinder chamber, to a wallsurface of the driving machine, it is considered to realize thedownsizing.

With this configuration, when the casing is attached to the wall surfaceof the driving machine, a minute space is formed between the wallsurface and the side plate. Since the space communicates with a space,where an underpressure is produced during the operation of the vacuumpump, through a gap between the rotor and the rotary shaft and a gapbetween the rotor and the side plate, the air in the above space isdrawn into the space by this underpressure, and the pressure of theabove space may become lower than the atmospheric pressure (i.e.,underpressure).

When the pressure of the space between the wall surface of the drivingmachine and the side plate becomes an underpressure, a flow of air inthe driving machine that flows into the above space through a bore nearthe bearing of the rotary shaft may be produced.

In the driving machine, abrasion powder due to sliding may exist, and itis considered that there is a problem that the durability of the drivingmachine decreases if the abrasion powder is attached to the bearing. Inthis case, the bearing can be changed to a sealed bearing, but in theconfiguration using the sealed bearing, there is the fifth problem thatit is said that the mechanical loss increases.

The invention is made in view of the above circumstances, and the fifthobject of the invention is to provide a vacuum pump so that the decreaseof the durability of the driving machine can be prevented withoutincreasing the mechanical loss.

In the small vacuum pump which operates a brake boosting device of anautomobile, since a small and lightweight rotor is used, the rotor isprovided movably in the axial direction of the rotary shaft withoutbeing fixed at all to the rotary shaft. Furthermore, because the rotoris provided at the front end part of the rotary shaft, when the rotor isrotated by driving the driving machine, it is possible that the rotormoves to the front end side of the rotary shaft with the rotation, andis protruded. Therefore, in the operation of the vacuum pump, since therotor contacts with the front side plate (front end side of the rotaryshaft), the rotor and the side plate are damaged due to the abrasion,and there is the sixth problem that the durability of the vacuum pump isdecreased.

The invention is made in view of the above circumstances, and the sixthobject of the invention is to prevent the damage of the rotor and theside plate and prevent the decrease of the durability of the vacuum pumpwith a simple configuration.

Solution to Problem

In order to achieve the first object, according to the presentinvention, there is provided a vacuum pump comprising rotary compressingelements in a casing, wherein the casing comprises a cylinder chamber inwhich the rotary compressing elements slide, an expansion chamber whichmakes a compressed air exhausted from the cylinder chamber to beexpanded, and an exhausting path which connects the cylinder chamber andthe expansion chamber, and at least one turning part is provided in theexhausting path.

According to this configuration, because at least one turning part isprovided in the exhausting path that connects the cylinder chamber andthe expansion chamber, the course length of the exhausting path can beformed to be longer. Therefore, when the compressed air exhausted fromthe cylinder chamber flows through the exhausting path having a longcourse length, since the air hits the wall surface of the exhaustingpath and is reflected diffusely, the sound energy of the compressed aircan be attenuated. Furthermore, because the compressed air attenuated inthe exhausting path flows into the expansion chamber and is furtherattenuated by being further expanded and scattered in the expansionchamber, the noise and the vibration in the air-exhausting can bereduced.

In the vacuum pump, the exhausting path and the expansion chamber areadjacently provided at a peripheral part of the cylinder chamber in thecasing.

According to this configuration, the exhausting path, the expansionchamber and the cylinder chamber can be integrally formed in the casing,and the upsizing of the vacuum pump can be inhibited.

In the vacuum pump a silence member formed of porous material isarranged in the exhausting path.

According to this configuration, because the compressed air that flowsthrough the exhausting path is rectified when the air passes the silencemember, and the sound energy of the compressed air is absorbed by thesilence member, the noise and the vibration in the air-exhausting can befurther reduced.

In the vacuum pump, the casing comprises a cylindrical liner which formsthe cylinder chamber, the cylindrical liner comprises an exhausting portwhich is connected to the exhausting path, a diameter of the exhaustingport at an inside of the cylinder chamber is larger than a diameter ofthe exhausting port at an outside of the cylinder chamber, and theexhausting port is formed to a taper shape whose diameter is reducedfrom the inside to the outside.

According to this configuration, since the exhausting port formed in thecylindrical liner is a taper hole, the pulsation of the compressed airexhausted from the cylinder chamber can be inhibited, and the noise andthe vibration in the air-exhausting with this pulsation can be reduced.

In the vacuum pump, a rotary shaft which drives the rotary compressingelements is comprised, and a front end part of the rotary shaft issupported with a bearing which is provided in the casing.

According to this configuration, because the shake of the rotary shaftis inhibited, the operating can be reduced.

In order to achieve the second object, according to the presentinvention, there is provided a vacuum pump comprising rotary compressingelements in a casing, wherein the casing comprises a casing body whichis formed of material whose thermal conductivity is higher than that ofthe rotary compressing elements, and a cylinder part which is pressfitted in the casing body and in which the rotary compressing elementsslide.

According to this configuration, since the casing is formed by pressfitting the cylinder part in the casing body, the casing can bedownsized. Because the casing body is formed of material whose thermalconductivity is higher than that of the rotary compressing elements,since the heat that occurred when the rotary compressing elements areoperated can be transmitted to the casing body immediately, the heatfrom the casing body can be dissipated sufficiently.

In the vacuum pump, the casing body and the cylinder part comprises acommunicating hole which communicates with the cylinder part bypenetrating through the casing body and the cylinder part, and while aninlet pipe is provided at the communicating hole, a front end of theinlet pipe is engaged with the communicating hole of the cylinder part.

According to this configuration, for example, when a material which hasa higher thermal expansion coefficient than that of the cylinder part isused for the casing body, even if the press fitting amount of thecylinder part is decreased due to thermal expansion, because the frontend of the inlet pipe is engaged with the communicating hole of thecylinder part, the cylinder part can be prevented from being rotated orfalling out.

In the vacuum pump, the cylinder part is formed of a material which hasa thermal expansion coefficient that is substantially equal to that ofthe rotary compressing elements.

According to this configuration, a change of the clearance between therotary compressing elements and the cylinder part with the temperaturechange can be inhibited, and the contact of the outer peripheral surfaceof the rotary compressing elements and the internal peripheral surfaceof the cylinder part can be prevented.

In the vacuum pump, in the casing body, the cylinder part is arranged ata position that is offset from the rotation center of the rotarycompressing elements, and the expansion chamber that communicates withthe cylinder part is formed at the peripheral part of the cylinder partat the side of the rotation center.

According to this configuration, it is not necessary to provide theexpansion chamber outside the casing body, the casing body can bedownsized, and thus the vacuum pump can be downsized.

In order to achieve the third object, according to the presentinvention, there is provided a vacuum pump comprising rotary compressingelements in a casing, wherein the casing comprises a casing body inwhich a cylinder chamber in which the rotary compressing elements slideis formed, an exhausting path which connects the cylinder chamber and anexhausting port, and an expansion chamber which is formed in theexhausting path, and the expansion chamber is provided at a peripheralpart of the cylinder chamber in the casing body.

According to this configuration, by providing the expansion chamber inthe exhausting path, since the compressed air flowing through theexhausting path is expanded and scattered in the expansion chamber andreflected diffusely by hitting the wall of the expansion chamber, thesound energy of the air is attenuated, and thereby the noise and thevibration in the air-exhausting can be reduced. Furthermore, because theexpansion chamber is provided at the peripheral part of the cylinderchamber in the casing body, the cylinder chamber and the expansionchamber can be formed integrally in the casing body and the upsizing ofthe compressing device can be inhibited.

In the vacuum pump, a Helmholtz resonance chamber which is branched fromthe exhausting path is connected to the expansion chamber.

The resonance chamber is connected to the expansion chamber through anorifice, and the cross section area and the length of the orifice andthe volume of the resonance chamber are set so that a resonancecounteracting the pressure pulsation of the compressed air that flowsthrough the exhausting path occurs. Therefore, by connecting theresonance chamber to the expansion chamber, the sound energy of the airexpanded in the expansion chamber is vibrated by an air spring in theorifice and the resonance chamber and attenuated. Therefore, thepressure pulsation of the air discharged from the rotary compressingelements can be reduced, and the noise and the vibration in theair-exhausting can be further reduced.

In the vacuum pump, the cylinder chamber is provided at a position thatis offset from a rotation center of the rotary compressing elements inthe casing body, and the expansion chamber and the resonance chamber areadjacently provided at the peripheral part of the cylinder chamber at aside of the rotation center.

According to this configuration, by arranging the cylinder chamber to beoffset from the rotation center of the rotary compressing elements, abig space at the peripheral part of the cylinder chamber at the side ofthe rotation center can be ensured in the casing body. Therefore, byadjacently providing the expansion chamber and the resonance chamber inthis space, it is not necessary to provide the expansion chamber and theresonance chamber outside the casing body, the casing body can bedownsized and thus the compressing device can be downsized.

In the vacuum pump, an intake path which leads air to the cylinderchamber is comprised, and an intake side expansion chamber which expandsthe air flowing in the intake path is provided in the intake path.

According to this configuration, by providing the intake side expansionchamber in the exhausting path, since the compressed air taken in thevacuum pump is expanded and scattered in the intake side expansionchamber, the sound energy of the air is attenuated, and thereby thenoise and the vibration in the air intake can be reduced.

In the vacuum pump, the intake side expansion chamber is formedadjacently to the expansion chamber at the peripheral part of thecylinder chamber in the casing body.

According to this configuration, by providing the expansion chamber andthe intake side expansion chamber at the peripheral part of the cylinderchamber, the cylinder chamber, the expansion chamber and the intake sideexpansion chamber can be formed integrally in the casing body and theupsizing of the compressing device can be inhibited.

In the vacuum pump, a desiccating agent is accommodated in the intakeside expansion chamber.

According to this configuration, since the water in the air flowing intothe cylinder chamber through the intake path can be removed, dry air canbe supplied to the cylinder chamber and dew condensation at the cylinderchamber and the rotary compressing elements can be prevented. Therefore,corrosion and freeze of the rotary compressing elements can be preventedand the life span of the compressing device can be extended.

In order to achieve the fourth object, according to the presentinvention, a vane-type compressing device, in which a rotor having anaxial bore where a driving shaft is inserted is rotatably included in acasing, and the rotor is provided with a plurality of vane slits inwhich a plurality of vanes are extendably accommodated, is characterizedin that the rotor is provided with a groove that links the vane slit toat least one of the axial bore and another vane slit.

According to this configuration, because the rotor is provided with thegroove that links the vane slit to at least one of the axial bore andanother vane slit, when an underpressure is almost produced in the vaneslit with the flying out of the vane, the occurrence of theunderpressure can be inhibited by making fluid from outside flow in, andwithout increasing the number of components, it becomes easy for thevane to fly out.

In this configuration, the groove may be provided on a side surface ofthe rotor. According to this configuration, the groove can be providedon the rotor with groove processing easily.

In this configuration, the groove may be a ring-like groove which linksthe deepest parts of all the vane slits. According to thisconfiguration, the occurrence of an underpressure due to the flying outof the vanes can be inhibited regardless of the positions of the vanesand without affecting the rotation balance of the rotor.

In this configuration, on the side surface of the rotor, a labyrinthpassage may be provided between the vane slits and the axial bore.According to this configuration, with the labyrinth passage between thevane slits and the axial bore, it becomes hard for the abrasion powderwhich occurs at the side of the vanes to flow to the center side of therotor, it can be prevented that the abrasion powder flows to the centerside of the rotor, and it can be prevented that the abrasion powder isattached to a bearing supporting the rotor.

In the configuration, it is preferred that the vane slits are offset topositions apart from the axial bore, and grooves that link the vaneslits and the axial bore extend into a linear shape along the radialdirection of the rotary shaft of the rotor and connect the deepest partsof the vane slits. According to this configuration, because the grooveswhich link the vane slits and the axial bore extend into a linear shapealong the radial direction of the rotary shaft of the rotor and connectthe deepest parts of the vane slits, in the configuration that the vaneslits are offset to positions apart from the axial bore, the vane slitsand the axial bore of the rotor can be linked at the shortest distance,and high pressure fluid at the center side of the rotor can be smoothlyintroduced into the vane slits. Therefore, the vanes can more easily flyout efficiently.

In order to achieve the fifth object, the present invention ischaracterized in that, a vacuum pump includes a casing attached to awall surface of a driving machine, a rotor rotationally driven by arotary shaft of the driving machine in the casing, and a plurality ofvanes extendably accommodated in the rotor, in the vacuum pump, thecasing includes a hollow cylinder chamber which is rotationally drivenby the rotor and has openings at the ends, and side plates which blockthe openings of the cylinder chamber, and a communicating hole, whichcommunicates a space which is formed between the side plate and the wallsurface of the driving machine, and another space whose pressure isabove the atmospheric pressure, is included.

According to this configuration, when the pressure of the space formedbetween the side plate and the wall surface of the driving machine isbelow the atmospheric pressure, since the air whose pressure is abovethe atmospheric pressure flows into the space through the communicatinghole, the pressure of the space is immediately restored to theatmospheric pressure (or above the atmospheric pressure). Therefore, byinhibiting that the air in the driving machine flows into the abovespace, a durability drop of the driving machine due to the abrasionpowder included in the air can be prevented.

In this configuration, the present invention is characterized in that,an expansion chamber formed in the exhausting path that links thecylinder chamber and the exhausting port is included in the casing atthe peripheral part of the cylinder chamber, and the communicating holeis formed at the expansion chamber. The present invention ischaracterized in that the communicating hole is formed at a positionthat is higher than the rotary shaft in the expansion chamber. Thepresent invention is characterized in that the driving machine includesa bearing which pivotally supports the rotary shaft, and thecommunicating hole is formed on the wall surface at a position that ishigher than the bearing.

In order to achieve the sixth object, in a vacuum pump that includes acasing which is attached to a driving machine, a hollow cylinder chamberwhich is formed in the casing and has openings at the two ends of thecasing, a rotor which is provided to be movable in the axial directionrelative to a rotary shaft of the driving machine and which isrotationally driven in the cylinder chamber with the rotary shaft, and apair of side plates which block the openings of the rotor, the presentinvention is characterized in that a push nut which regulates themovement of the rotor to the front end of the rotary shaft is providedto the rotary shaft.

According to this configuration, with the push nut provided to therotary shaft, the movement of the rotor to the front end side of therotary shaft is regulated. Therefore, by preventing the contact of therotor and the front side plate with a simple configuration, the abrasionof the rotor and the side plate is inhibited and the durability of thevacuum pump can be improved. Furthermore, because the push nut is easilyattached to the rotary shaft in comparison with other fastening meanssuch as bolts, the movement of the rotor to the front end side of therotary shaft can be prevented with an easy and short-time operation.

In this configuration, the present invention is characterized in that,the rotor is inserted into the rotary shaft until the rotor abutsagainst the side plate located at the side of the driving machine, andin this state, by pressing the push nut against the end surface of therotor 527 until a predetermined reference value is exceeded, the pushnut is locked to the rotary shaft. According to this configuration, thepositioning of the rotor relative to the rotary shaft can be performedeasily and the assembly of the pump can be performed in a short timeeven if there is not an expert.

The present invention is characterized in that the rotary shaft includesa locking part, to which a plurality of claw parts of the push nut arelocked, and a diameter-reduced part whose diameter is smaller than thatof the locking part, at the front end part, and the diameter of thediameter-reduced part is formed to be substantially equal to the insidediameter of an opening surrounded by the front ends of the plurality ofclaw parts of the push nut. According to this configuration, because thediameter of the diameter-reduced part is formed to be substantiallyequal to the inside diameter of the opening surrounded by the front endsof the plurality of claw parts of the push nut, by making the push nutto move along the diameter-reduced part, the push nut can be guided tothe locking part without being inclined relative to the rotary shaft.Therefore, by pressing the push nut guided to the locking part againstthe rotor, the likelihood of failing to install the push nut due to theinclination of the push nut can be reduced, and while the operationprocedure is simplified, the operation time can be shortened.

The present invention is characterized in that, a recess is formed atthe front end surface of the rotor around the axial bore where therotary shaft is inserted, and the push nut is locked to the rotary shaftin the recess. According to this configuration, without making the frontend part of the rotary shaft to be protruded from the front end surfaceof the rotor, the push nut can be locked to the rotary shaft and theconfiguration of the vacuum pump can be simplified.

Advantageous Effects of Invention

According to the present invention, because at least one turning part isprovided in the exhausting path that connects the cylinder chamber andthe expansion chamber, the course length of the exhausting path can beformed to be longer. Therefore, when the compressed air exhausted fromthe cylinder chamber flows through the exhausting path having a longcourse length, since the air hits the wall surface of the exhaustingpath and is reflected diffusely, the sound energy of the compressed aircan be attenuated. Furthermore, because the compressed air attenuated inthe exhausting path flows into the expansion chamber and is furtherattenuated by being further expanded and scattered in the expansionchamber, the noise and the vibration in the air-exhausting can bereduced.

According to the present invention, since the casing is formed by pressfitting the cylinder part in the casing body, the casing can bedownsized. Because the casing body is formed of material whose thermalconductivity is higher than that of the rotary compressing elements,since the heat that occurred when the rotary compressing elements areoperated can be transmitted to the casing body immediately, the heatfrom the casing body can be dissipated sufficiently.

According to the present invention, by providing the expansion chamberin the exhausting path, since the compressed air flowing through theexhausting path is expanded and scattered in the expansion chamber andreflected diffusely by hitting the wall of the expansion chamber, thesound energy of the air is attenuated, and thereby the noise and thevibration in the air-exhausting can be reduced. Furthermore, because theexpansion chamber is provided at the peripheral part of the cylinderchamber in the casing body, the cylinder chamber and the expansionchamber can be formed integrally in the casing body and the upsizing ofthe compressing device can be inhibited.

According to the present invention, because the rotor is provided withthe groove that links the vane slit to at least one of the axial boreand another vane slit, without increasing the number of components, itbecomes easy for the vane to fly out.

According to the present invention, because the communicating hole thatcommunicates the space which is formed between the side plate and thewall surface of the driving machine and another space whose pressure isabove the atmospheric pressure is included, when the pressure of thespace is below the atmospheric pressure, since the air whose pressure isabove the atmospheric pressure flows into the space through thecommunicating hole, the pressure of the space is immediately restored tothe atmospheric pressure (or above the atmospheric pressure). Therefore,by inhibiting that the air in the driving machine flows into the abovespace, a durability drop of the driving machine due to the abrasionpowder included in the air can be prevented.

According to the present invention, with the push nut provided to therotary shaft, the movement of the rotor to the front end side of therotary shaft is regulated. Therefore, by preventing the contact of therotor and the front side plate with a simple configuration, the abrasionof the rotor and the side plate is inhibited and the durability of thevacuum pump can be improved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is schematic diagram of a brake device in which a vacuum pumpaccording to the embodiment of the invention to achieve the first objectis used.

FIG. 2 is a side partial sectional view of the vacuum pump.

FIG. 3 is a figure of the vacuum pump when viewed from the front side.

FIG. 4 is a partially enlarged view of FIG. 2 which shows an exhaustingport that is formed in a cylindrical liner.

FIG. 5 is a list which records noise levels corresponding to differentconfigurations.

FIG. 6 is a side partial sectional view of a vacuum pump according toanother embodiment.

FIG. 7 is a side partial sectional view of a vacuum pump according tothe embodiment to achieve the second object.

FIG. 8 is a figure of the vacuum pump viewed from the front side.

FIG. 9 is a perspective view which shows the back side of a case body.

FIG. 10A is a figure which shows a coupling structure of an electricmotor and a pump body, and FIG. 10B is a variation of the couplingstructure.

FIG. 11 is a side partial sectional view of a vacuum pump according tothe embodiment to achieve the third object.

FIG. 12 is a figure of the vacuum pump when viewed from the front side.

FIG. 13 is an III-III sectional view of FIG. 12.

FIG. 14 is a side partial sectional view of a vacuum pump according toanother embodiment.

FIG. 15 is a side partial sectional view of a vacuum pump according toanother embodiment.

FIG. 16 is a side partial sectional view of a vacuum pump according tothe first embodiment of the invention to achieve the fourth object.

FIG. 17 is a figure of the vacuum pump when viewed from the front side.

FIG. 18A is a figure which shows a side surface of a rotor with theneighboring configuration, and FIG. 18B shows a B-B section of FIG. 18A.

FIG. 19A is a figure which shows a side surface of a rotor according tothe second embodiment with the neighboring configuration, and FIG. 19Bis a B-B sectional view of FIG. 19A.

FIG. 20A is a figure which shows a side surface of a rotor according tothe third embodiment with the neighboring configuration, and FIG. 20B isa B-B sectional view of FIG. 20A.

FIG. 21 is a figure which enlarges and shows an output shaft of theelectric motor with the neighboring configuration.

FIG. 22A is a figure which shows a side surface of a rotor according tothe fourth embodiment with the neighboring configuration, and FIG. 22Bis a B-B sectional view of FIG. 22A.

FIG. 23 is a figure which describes a variation.

FIG. 24 is a side partial sectional view of a vacuum pump according tothe embodiment to achieve the fifth object.

FIG. 25 is a figure of the vacuum pump when viewed from the front side.

FIG. 26 is a rear view of a casing body.

FIG. 27 is a figure which describes a flow of air.

FIG. 28 is schematic diagram of a brake device in which a vacuum pumpaccording to the embodiment of the invention to achieve the sixth objectis used.

FIG. 29 is a side partial sectional view of the vacuum pump.

FIG. 30 is a figure of the vacuum pump when viewed from the front side.

FIG. 31 is an exploded perspective view which shows a coupling structureof a rotor and an output shaft.

FIG. 32 is a figure which shows a shape of the front end part of therotary shaft and a shape of a push nut.

FIGS. 33A to 33C are figures which describe assembling procedures of arotor.

DESCRIPTION OF EMBODIMENTS

Below, preferred embodiments of the invention are described withreference to the figures.

FIG. 1 is a schematic diagram of a brake device 100 in which a vacuumpump 1 according to the embodiment of the invention to achieve the firstobject is used as a vacuum source. For example, the brake device 100includes front brakes 2A and 2B which are attached to the right and leftfront wheels of a vehicle such as an automobile, and rear brakes 3A and3B which are attached to the right and left rear wheels.

These brakes are connected with a master cylinder 4 via brake tubes 9,respectively, and each brake is operated with an oil pressure which issent through the brake tube 9 from the master cylinder 4.

The brake device 100 further includes a brake booster 6 (brake boostingdevice) which is connected with a brake pedal 5, and a vacuum tank 7 andthe vacuum pump 1 is serially connected to the brake booster 6 throughan air tube 8. The brake booster 6 is adapted to boost the pedal forceof the brake pedal 5 using an underpressure in the vacuum tank 7, andwhen a piston (not shown in the figure) of the master cylinder 4 ismoved by a small pedal force, an enough braking power will be got.

The vacuum pump 1 is arranged in an engine room of the vehicle, andexhausts air in the vacuum tank 7 to the outside of the vehicle so thatthere becomes a vacuum in the vacuum tank 7. The use range of the vacuumpump 1 used for automobiles or the like is, for example, −60 kPa to −80kPa. FIG. 2 is a side partial sectional view of the vacuum pump 1, andFIG. 3 is a figure of the vacuum pump 1 of FIG. 2 when viewed from thefront side of the vacuum pump 1 (the right side in the figure). However,FIG. 3 illustrates a state that those members such as a pump cover 24and a side plate 26 are removed in order to show the configuration of acylinder chamber S. In the following, for the convenience ofdescription, the directions respectively indicated by the arrows in theupper parts of FIGS. 2 and 3 are the up, down, front, rear, right andleft directions of the vacuum pump 1. The front-rear direction is anaxial direction, and the right-left direction is a widthwise direction.

As shown in FIG. 2, the vacuum pump 1 includes an electric motor(driving machine) 10 and a pump body 20 which is operated by using theelectric motor 10 as a driving source, and the electric motor 10 and thepump body 20 are fixed to and supported by a vehicle body of, forexample, an automobile in an integrally connected state.

The electric motor 10 has an output shaft (rotary shaft) 12 whichextends substantially from the center of one end (front end) of a case11, which is formed into a substantially cylindrical shape, towards theside of the pump body 20 (front side). The output shaft 12 functions asa driving shaft for driving the pump body 20, and the output shaft 12rotates around a rotation center X1 extending in the front-reardirection. A front end part 12A of the output shaft 12 is formed into aspline shaft and is engaged with a spline groove 27D, which is formedinto a part of an axial bore 27A which is a through hole in the axialdirection of the rotor 27 of the pump body 20, so that the output shaft12 and the rotor 27 are connected to be integrally rotatable.

When a power supply (not shown in the figure) is switched ON, the outputshaft 12 of the electric motor 10 rotates in an arrow R direction(counterclockwise direction) in FIG. 3, and thereby the rotor 27 isrotated in the same direction (arrow R direction) around the rotationcenter X1.

The case 11 includes a case body 60, which is formed to a bottomedcylindrical shape, and a cover body 61 which blocks the opening of thecase body 60, and the case body 60 is formed by bending a peripheralpart 60A of the case body 60 outwards. The cover body 61 is integrallyformed by including a disk part (wall surface) 61A which is formed tohave substantially the same diameter as that of the opening of the casebody 60, a cylinder part 61B which is connected to the fringe of thedisk part 61A and is fitted into the internal peripheral surface of thecase body 60, and a flexed part 61C which is formed by bending outwardsthe fringe of the cylinder part 61B, the disk part 61A and the cylinderpart 61B enter into the case body 60, and the flexed part 61C abutsagainst and is fixed to the peripheral part 60A of the case body 60.Thereby, in the electric motor 10, one end (front end) of the case 11 iscaved inwards, and a fitting cavity 63, which the pump body 20 isattached to in a pillbox fitting manner, is formed.

Approximately in the center of the disk part 61A, a through hole 61Dwhere the output shaft 12 penetrates and a circular bearing holding part61E which extends inside of the case body 60 around the through hole 61Dare formed, and the outer ring of a bearing 62 that pivotally supportsthe front side of the above output shaft 12 is held by the internalperipheral surface 61F of the bearing holding part 61E.

The pump body 20 includes, as shown in FIG. 2, a casing body 22 which isfitted into the fitting cavity 63 which is formed at the front side ofthe case 11 of the electric motor 10, a cylindrical liner 23 which isarranged in the casing body 22 and forms a cylinder chamber S, and apump cover 24 which covers the casing body 22 from the front side. Inthis embodiment, a casing 31 of the vacuum pump 1 is formed by includingthe casing body 22, the cylindrical liner 23 and the pump cover 24.

The casing body 22 uses, for example, metal materials such as aluminumwhose thermal conductivity is high, and as shown in FIG. 3, the shape ofthe casing body 22, when viewed from front, is formed to a substantiallyrectangular shape which is longer in the up-down direction with theabove-mentioned rotation center X1 as an approximate center. Acommunicating hole 22A, which communicates with the cylinder chamber Swhich the casing body 22 is provided with, is formed in the upper partof the casing body 22, and an absorbing nipple 30 is press fitted to thecommunicating hole 22A. As shown in FIG. 2, the absorbing nipple 30 is adirect pipe which extends upwards, and a pipe or a tube which suppliesunderpressure air from an external equipment (for example, the vacuumtank 7 (refer to FIG. 1)) is connected to one end 30A of the absorbingnipple 30.

A bore 22B around a central axis X2 which extends in the front-reardirection is formed in the casing body 22, and a cylindrical liner 23which is formed to a cylindrical shape is press fitted into the bore22B. Instead of press fitting the cylindrical liner 23 into the bore 22Bof the casing body 22, it is also possible to cast the casing body 22 ina state that the cylindrical liner 23 was cast in. The central axis X2is parallel with the rotation center X1 of the output shaft 12 of theabove-mentioned electric motor 10, and as shown in FIG. 3, is offset tothe upper left side relative to the rotation center X1. In thisconfiguration, the central axis X2 is offset so that the outerperipheral surface 27B of the rotor 27 around the rotation center X1 isadjacent to the internal peripheral surface 23A of the cylindrical liner23 that is formed around the central axis X2.

The cylindrical liner 23 is formed of the same metal materials (in thepresent embodiment, iron) as that of the rotor 27, and for example,electroless nickel plating process is applied on the internal peripheralsurface 23A of the cylindrical liner 23 so that the hardness of theinternal peripheral surface 23A is raised.

In this embodiment, because the cylindrical liner 23 can be accommodatedin the length range of the front-rear direction of the casing body 22 bypress fitting (or casting in) the cylindrical liner 23 into the bore 22Bwhich is formed in the casing body 22, the cylindrical liner 23 isprevented from being protruded from the casing body 22 and the casingbody 22 can be downsized.

Furthermore, the casing body 22 is formed of material whose thermalconductivity is higher than that of the rotor 27.

Thereby, since the heat that is generated when the rotor 27 and vanes 28are rotationally driven can be transmitted to the casing body 22immediately, the heat from the casing body 22 can be dissipatedsufficiently.

An opening 23B which is coupled with the communicating hole 22A of theabove described casing body 22 and the cylinder chamber S is formed atthe cylindrical liner 23, and the air passing through the absorbingnipple 30 is supplied to the cylinder chamber S through thecommunicating hole 22A and the opening 23B. At the lower part of thecasing body 22 and the cylindrical liner 23, exhausting ports 22C and23C, which penetrate the casing body 22 and the cylindrical liner 23 andwhere the air compressed in the cylinder chamber S is exhausted, areprovided. The exhausting port 23C which the cylindrical liner 23 isprovided with will be described later.

Side plates 25 and 26 which block the openings of the cylinder chamberS, respectively, are disposed at the rear end and the front end of thecylindrical liner 23.

The diameter of the side plates 25 and 26 is set to be larger than theinside diameter of the internal peripheral surface 23A of thecylindrical liner 23. The side plates 25 and 26 are pressed against thefront end and the rear end of the cylindrical liner 23, respectively, bybeing biased by wave washers 25A and 26A. Thereby, the sealed cylinderchamber S is formed inside the cylindrical liner 23 except the opening23B which is coupled to the absorbing nipple 30 and the exhausting ports23C and 22C. It is also possible in configuration to provide sealingrings in substitution for the wave washers 25A and 26A.

In the cylinder chamber S, the rotor 27 is disposed. The rotor 27 has acylindrical column shape which extends along the rotation center X1 ofthe electric motor 10, and has an axial bore 27A through which theoutput shaft 12 which is a driving shaft of the pump body 20 isinserted. Meanwhile, at positions away from the axial bore 27A in theradical direction, a plurality of guide grooves 27C are provided aroundthe axial bore 27A by being spaced in the peripheral direction with anequal angular interval. A spline groove 27D, which is engaged with thespline shaft that is provided at the front end part 12A of the outputshaft 12, is formed at a part of the axial bore 27A, and the rotor 27and the output shaft 12 is adapted to be spline connected.

In this embodiment, at the front end of the rotor 27, a columnar recess27F whose diameter is larger than that of the axial bore 27A is formedaround the axial bore 27A, a push nut 70 is attached to the front end ofthe output shaft 12 which extends into the recess 27F, and the movementof the rotor 27 to the front end side of the output shaft 12 isregulated by the push nut 70.

The length in the front-rear direction of the rotor 27 is set to besubstantially equal to the length of the cylinder chamber S of thecylindrical liner 23, namely, the distance between the mutually opposedinside surfaces of the above-mentioned two pieces of side plates 25 and26, and the space between the rotor 27 and the side plates 25 and 26 aresubstantially blocked.

The outer diameter of the rotor 27 is set so that, as shown in FIG. 3,the outer peripheral surface 27B of the rotor 27 keeps a minuteclearance from a part among the internal peripheral surface 23A of thecylindrical liner 23 that is located at the lower right side. Thereby,in the cylinder chamber S partitioned by the side plates 25 and 26, asshown in FIG. 3, a space of a crescent shape is formed between the outerperipheral surface 27B of the rotor 27 and the internal peripheralsurface 23A of the cylindrical liner 23.

The rotor 27 is provided with a plurality of (in this example, fivepieces) vanes 28 which partition the crescent space. The vane 28 isformed into a board shape, and the length in the front-rear direction isset to be substantially equal to the distance between the mutuallyopposed inside surfaces of the two pieces of side plates 25 and 26, likethe rotor 27. These vanes 28 are disposed to be extendable from theguide grooves 27C which the rotor 27 is provided with. The vanes 28 areprotruded outwards along the guide grooves 27C by a centrifugal forcewith the rotation of the rotor 27 so that the front ends of the vanes 28abut with the internal peripheral surface 23A of the cylindrical liner23. Thereby, the above-mentioned crescent space is partitioned into 5compression chambers P surrounded by two pieces of mutually adjacentvanes 28 and 28, the outer peripheral surface 27B of the rotor 27 andthe internal peripheral surface 23A of the cylindrical liner 23. Thesecompression chambers P rotates in the same direction with the rotationof the arrow R direction of the rotor 27 with the rotation of the outputshaft 12, and the capacity of each of these compression chambers Pbecomes bigger at positions near the opening 23B, and becomes smaller atpositions near the exhausting port 23C. That is, with the rotation ofthe rotor 27 and the vanes 28, the air taken in one compression chamberP from the opening 23B rotates and is compressed with the rotation ofthe rotor 27, and is discharged from the exhausting port 23C. In thisconfiguration, the rotary compressing elements are formed by includingthe rotor 27 and the plurality of vanes 28.

The pump cover 24 is arranged to the front side plate 26 via the wavewasher 26A, and is fixed to the casing body 22 with a bolt 66. On thefront of the casing body 22, as shown in FIG. 3, a sealing groove 22D isformed by surrounding the cylindrical liner 23, an expansion chamber 33and an exhausting path 40 to be described below, and an annular sealingmember 67 (FIG. 2) is arranged to the sealing groove 22D. An exhaustingport 24A is provided in the pump cover 24 at a position corresponding tothe expansion chamber 33. The exhausting port 24A is intended to exhaustthe air which flows into the expansion chamber 33 to the outside of thedevice (the outside of the vacuum pump 1), and a check valve 29 forpreventing the countercurrent of air from the outside of the device intothe pump is attached to the exhausting port 24A.

As mentioned above, the vacuum pump 1 is formed by coupling the electricmotor 10 and the pump body 20, and the rotor 27 connected to the outputshaft 12 of the electric motor 10 and the vanes 28 slide in thecylindrical liner 23 of the pump body 20. Therefore, it is important toassemble the pump body 20 in accordance with the rotation center X1 ofthe output shaft 12 of the electric motor 10.

Therefore, in this embodiment, the fitting cavity 63, which is centeredon the rotation center X1 of the output shaft 12, is formed at one endof the case 11 of the electric motor 10. On the other hand, on the backof the casing body 22, as shown in FIG. 2, a cylindrical fitting part22F is integrally formed to be protruded backwards around the cylinderchamber S. The fitting part 22F is formed concentrically with therotation center X1 of the output shaft 12 of the electric motor 10, andis formed so that the outer edge of the fitting part 22F is engaged withthe fitting cavity 63 of the electric motor 10 in a pillbox manner.Thereby, with this configuration, only by fitting the fitting part 22Fof the casing body 22 into the fitting cavity 63 of the electric motor10, the central locations can be easily put together and the assembly ofthe electric motor 10 and the pump body 20 can be easily performed.Further, on the back of the casing body 22, a sealing groove 22E isformed around the fitting part 22F, and a circular sealing member 35 isarranged to the sealing groove 22E.

With the vane-type vacuum pump 1, because air is compressed when therotor 27 and the vanes 28 are rotated in the cylinder chamber S, thecompressed air is discharged intermittently from the exhausting ports23C and 22C of the cylinder chamber S. Therefore, since pressurepulsation occurs at a constant basic frequency in the exhausting ports23C and 22C of the cylinder chamber S, the noise and vibration due tothis pressure pulsation may occur.

In order to prevent the noise and vibration, the exhausting path 40which communicates with the exhausting ports 23C and 22C of the cylinderchamber S and the expansion chamber 33 which makes the compressed airwhich is introduced through the exhausting path 40 to be expanded areformed in the casing body 22.

In this embodiment, the cylindrical liner 23 is formed in the casingbody 22, as shown in FIG. 3, by offsetting the central axis X2 of thecylindrical liner 23 to the upper left side relative to the rotationcenter X1. Therefore, in the casing body 22, a big space in thedirection opposite to that the cylindrical liner 23 is offset can besecured, and the above described exhausting path 40 and the expansionchamber 33 are formed in this space along the peripheral part of thecylindrical liner 23. Thus, because the exhausting path 40 and theexpansion chamber 33 can be integrally formed in the casing body 22, itis not necessary to provide the exhausting path 40 and the expansionchamber 33 outside the casing body 22, the casing body 22 can bedownsized and the vacuum pump 1 can be downsized.

The expansion chamber 33 is a space where the compressed air which flowsin through the exhausting path 40 is expanded and scattered. After thecompressed air which flows into the expansion chamber 33 is expanded andscattered, the air hits the inner wall of the expansion chamber 33 andis reflected diffusely. Since the sound energy of the compressed air isattenuated, the noise and the vibration in the air-exhausting arereduced. In the embodiment, the expansion chamber 33 is formed as a bigclosed space along the peripheral part of the cylindrical liner 23 froma position below the cylindrical liner 23 to a position above the outputshaft 12, and communicates with the exhausting port 24A which is formedin the pump cover 24. The exhausting port 24A is provided so that theflow of the discharged air is substantially perpendicularly changedrelative to the flowing direction (arrow M direction) of the air in theexhausting path 40 and the expansion chamber 33, and the sound energycan be decreased by changing the direction of the flow of the air.

The exhausting path 40 is a space whose course cross section is formedto be smaller than that of the expansion chamber 33, and the compressedair that flows into the exhausting path 40 positively hits the innerwall of the exhausting path 40 so that the sound energy is decreased. Inthis embodiment, the casing body 22 includes a separating wall 41 whichis provided outside the cylinder chamber S, and the exhausting path 40is formed as a space partitioned by the separating wall 41.

In particular, the separating wall 41 is formed into an arc shape whichis substantially concentric with the cylinder chamber S, and one end 41Aof the separating wall 41 is connected to the bore 22B at a positionbeyond the exhausting port 22C. The other end 41B of the separating wall41 extends to a position so that the space of the exhausting path 40 isnot blocked.

Therefore, the exhausting path 40 includes an inside course 40A which isformed between the separating wall 41 and the cylinder chamber S andinto which the compressed air from the exhausting port 22C flows, and anoutside course 40B which is formed outside the separating wall 41 andwhich is connected to the above described expansion chamber 33, and aturning part 40C is formed at the side of the other end 41 B of theseparating wall 41 to couple the inside course 40A with the outsidecourse 40B. Therefore, the compressed air exhausted from the cylinderchamber S through the exhausting ports 22C and 23C, as shown by thearrow M, flows through the inside course 40A, turns at the turning part40C, flows through the outside course 40B, and flows into the expansionchamber 33.

With this configuration, since the exhausting path 40 includes theturning part 40C formed by the separating wall 41, the course length ofthe exhausting path 40 can be formed to be longer. When the compressedair flowing through the exhausting path 40 flows through the exhaustingpath 40 having a long course length, since the air hits the wall surfaceof the exhausting path 40 and is reflected diffusely, the sound energyof the compressed air can be attenuated. In this case, when the coursecross section of the exhausting path 40 is an oblong shape that extendsaxially so that the surface area of the wall surface of the exhaustingpath 40 is increased as much as possible, the opportunity that the airhits the wall surface is increased, and the silence effect is increased.

Furthermore, because the compressed air attenuated in the exhaustingpath 40 then flows into the expansion chamber 33 and is furtherattenuated by being further expanded and scattered in the expansionchamber 33, the noise and the vibration in the air-exhausting can bereduced.

In this embodiment, the exhausting path 40 includes silence members 44Aand 44B at the inlet part of the inside course 40A and the exhaustingport part of the outside course 40B, respectively. These silence members44A and 44B are, for example, porous members which are formed to asubstantially rectangular shape by making metal particles such as copperor stainless steel to be sintered. These silence members 44A and 44B arefixed by being inserted into grooves 45 and 46 provided at the sidewallsof the inside course 40A and the outside course 40B, respectively.

According to this configuration, because the compressed air that flowsthrough the exhausting path 40 is rectified when the air passes themicro spaces of the silence members 44A and 44B, and the sound energy ofthe compressed air is inleted by the silence members, the sound energyof the compressed air that flows into the expansion chamber 33 from theexhausting path 40 can be attenuated, and the noise and the vibration inthe air-exhausting can be further reduced. In this case, by arrangingone silence member 44A near the exhausting port 22C and the othersilence member 44B near the expansion chamber 33, a bigger silenceeffect is achieved.

FIG. 4 is a partially enlarged view of FIG. 2 which shows the exhaustingport 23C that is formed in the cylindrical liner 23. As mentioned above,it is found that the noise and the vibration that occur in theair-exhausting are caused by the pulsation of the compressed air fromthe exhausting ports 23C and 22C of the cylinder chamber S with therotation of the rotor 27 and the vanes 28.

To reduce this pressure pulsation, after changing the shape of theexhausting port 23C in various ways and measuring noise levels, theapplicant realized that, as shown in FIG. 4, when the inside pore sized1 of the exhausting port 23C at the cylinder chamber S is bigger thanthe outside pore size d2 and the exhausting port 23C becomes a taperhole which has a taper surface 23C1 whose diameter is reduced from thepore size d1 to d2, the noise is inhibited.

In particular, the inside pore size d1 of the exhausting port 23C at thecylinder chamber S is set to be substantially the same as the pore sized3 of the exhausting port 22C of the casing body 22 (in the presentembodiment, 10.5 mm in diameter). It is desirable that the outside poresize d2 is set to be around 70% of the above described pore size d1, or7 mm in diameter in the present embodiment. The angle α of the tapersurface 23C1 is set to 120°.

With this configuration, since the inside pore size d1 of the exhaustingport 23C formed in the cylindrical liner 23 at the cylinder chamber S isbigger than the outside pore size d2, and the exhausting port 23C is ataper hole which has a taper surface 23C1 whose diameter is reduced frominside to outside, without extremely raising the exhausting resistancefrom the exhausting port 23C, the exhausting volume from the cylinderchamber S can be squeezed. Therefore, the pulsation of the compressedair exhausted from the cylinder chamber can be inhibited, and the noiseand vibration in the air-exhausting with this pulsation can be reduced.

Next, the reduction effect of noise level with the above describedconfiguration is described.

FIG. 5 records noise levels corresponding to different configurations.These noise levels are obtained by arranging a plurality of (forexample, at ten positions) microphones for measurement around the vacuumpump 1, measuring noise levels with each of the microphones in thisstate when the vacuum pump 1 is operated, and averaging thesemeasurements.

According to the FIG. 5, by providing the exhausting path 40, the noiselevel (63.4 dB) is lower by 8.3 dB (approximately 12%) than the noiselevel (71.7 dB) of the configuration that only the expansion chamber 33is provided. By placing the silence members 44A and 44B in theexhausting path 40, the noise level (59.7 dB) is further lower by 3.7 dB(approximately 6%), and when the exhausting port 23C is added in theconfiguration as the taper hole, as a result, the noise level (58.6 dB)is further lower by 1.1 dB (approximately 1.9%).

Thus, by taking various measures, the vacuum pump 1 whose noise level isreduced can be realized, and when the vacuum pump 1 is carried on avehicle, discomfort due to the noise of the vacuum pump 1 can beinhibited.

According to the present embodiment, the casing body 22 includes thecylinder chamber S where the rotor 27 and the vanes 28 slides, theexpansion chamber 33 which makes the compressed air that is exhaustedfrom the cylinder chamber S to be expanded, and the exhausting path 40which connects the expansion chamber 33 and the cylinder chamber S, andat least one turning part 40C is provided in the exhausting path 40.Therefore, the course length of the exhausting path 40 can be formed tobe longer, since the exhausting path 40 is turned at the turning part40C. Therefore, when the compressed air exhausted from the cylinderchamber S flows through the exhausting path 40 having a long courselength, since the air hits the wall surface of the exhausting path 40and is reflected diffusely, the sound energy of the compressed air canbe attenuated. Furthermore, because the compressed air attenuated in theexhausting path 40 flows into the expansion chamber 33 and is furtherattenuated by being further expanded and scattered in the expansionchamber 33, the noise and the vibration in the air-exhausting can bereduced.

According to the present embodiment, the exhausting path 40 and theexpansion chamber 33 are adjacently provided at the peripheral part ofthe cylinder chamber S in the casing body 22. Therefore, the exhaustingpath 40, the expansion chamber 33 and the cylinder chamber S can beintegrally formed in the casing body 22, and the upsizing of the vacuumpump 1 can be inhibited.

According to the present embodiment, because the silence members 44A and44B formed of porous material are arranged in the exhausting path 40,while the compressed air flowing through the exhausting path 40 isrectified when the compressed air passes the silence members 44A and44B, the sound energy of the compressed air is inleted by the silencemembers 44A and 44B. Therefore, the noise and the vibration in theair-exhausting can be further reduced.

According to the present embodiment, the casing body 22 and thecylindrical liner 23 forming the cylinder chamber S are included, thecylindrical liner 23 includes the exhausting port 23C connected to theexhausting path 40, the inside pore size d1 of the exhausting port 23Cat the cylinder chamber S is bigger than the outside pore size d2, andthe exhausting port 23C is formed to the taper hole which has the tapersurface 23C1 whose diameter is reduced from inside to outside.Therefore, the pulsation of the compressed air exhausted from thecylinder chamber S can be inhibited, and the noise and vibration in theair-exhausting with this pulsation can be reduced.

Then, another embodiment is described.

FIG. 6 is a side partial sectional view of a vacuum pump according toanother embodiment.

A vacuum pump 80 according to the embodiment differs in configurationfrom the above described embodiment in that a pilot bearing, whichsupports the front end part of the output shaft 12 which rotates therotor 27, is included. The same components are given the same symbolsand their description is omitted.

In this embodiment, the output shaft 12 integrally includes a bearingattaching part 12A1, to which a pilot bearing 81 is attached, at thefront end part 12A, and the bearing attaching part 12A1 extends beyondthe pump body 20 by penetrating through a through hole 26B of the frontside plate 26 and a bearing holding hole 84A of a pump cover 84. On theinner surface of the pump cover 84, the bearing holding hole 84A isformed, and the pilot bearing 81 is held in the bearing holding hole84A. With this configuration, because the bearing holding hole 84A,which has such a depth that the pilot bearing 81 can be held, is formedon the inner surface, the board of the pump cover 84 is thickly formed.

According to this configuration, because the front end part of theoutput shaft 12 is supported by the pilot bearing 81, by inhibiting theshake of the output shaft 12, the rotor 27 and the vanes 28 can berotated stably in the cylinder chamber S. Therefore, the sound of therotor 27 and the vanes 28 that are operating can be reduced.

The preferred embodiments for performing the present invention aredescribed as above, but the present invention is not limited to thepreviously described embodiments, and various modifications and changesare possible based on the technical thought of the present invention.For example, in this embodiment, the exhausting path 40 is formed byincluding one turning part 40C, but it is also possible to provide twoor more turning parts as long as they can be installed. Further, in thisembodiment, it is described that two silence members 44A and 44B arearranged in the exhausting path 40, but three or more silence membersmay be included. Further, the sintered metal silence members which aremade by sintering metal particles are exemplified as the silencemembers, but if a temperature condition is set, silence members formedof sintered resin can be arranged.

FIG. 7 is a side partial sectional view of a vacuum pump 1 according tothe embodiment of the invention to achieve the second object. FIG. 8 isa figure of the vacuum pump 101 of FIG. 7 when viewed from the frontside of the vacuum pump 101 (the right side in the figure above).However, FIG. 8 illustrates a state that those members such as a pumpcover 124 and a side plate 126 are removed in order to show theconfiguration of a cylinder chamber S. In FIG. 8, a state that anattaching member 140 is removed is shown.

In the following, for the convenience of description, the directionsrespectively indicated by the arrows in the upper parts of FIGS. 7 and 8are the up, down, front, rear, right and left directions of the vacuumpump 101. The front-rear direction is an axial direction, and theright-left direction is an widthwise direction.

The vacuum pump 101 shown in FIG. 7 is a rotary vane-type vacuum pump,and, for example, is used as a vacuum source of a brake boosting device(not shown in the figure) of an automobile or the like. In this case,the vacuum pump 101 is usually arranged in an engine room and isconnected with pipes to the brake boosting device through a vacuum tank(not shown in the figure). The use range of the vacuum pump 101 used forautomobiles or the like is, for example, −60 kPa to −80 kPa.

As shown in FIG. 7, the vacuum pump 101 includes an electric motor 110and a pump body 120 which is arranged to the electric motor 110, and theelectric motor 110 and the pump body 120 are fixed to and supported by avehicle body 150 of, for example, an automobile in an integrallyconnected state by an attaching member 140.

The attaching member 140 includes an attaching plate 141 which isprovided with a rectangular projecting slot 141A that extends in thewidthwise direction of the pump body 120, and vibration proof rubbers142 and 142 which are fixed to the front end and the rear end of theattaching plate 141, respectively. These vibration proof rubbers 142 and142 are held by being fitted into bores formed on the vehicle body. Theattaching plate 141 is fixed with a bolt 143 onto the bottom surface ofthe pump body 120 at the projecting slot 41A.

The electric motor 110 has an output shaft 112 which extendssubstantially from the center of one end (front end) of a case 111,which is formed into a substantially cylindrical shape, towards the sideof the pump body 120 (front side). The output shaft 112 rotates around arotation center X1 that extends in the front-rear direction. A splinepart 112B, which is fitted into a rotor 127 of the pump body 120 to bedescribed below and turns and stops the rotor 127, is formed at thefront end part 112A of the output shaft 112. By providing a key on theoutside surface of the output shaft 112, the skidding of the rotor 127can be prevented.

When a power supply (not shown in the figure) is switched ON, the outputshaft 112 of the electric motor 110 rotates in an arrow R direction(counterclockwise direction) in FIG. 8, and thereby the rotor 127 isrotated in the same direction (arrow R direction) around the rotationcenter X1.

The case 111 includes a case body 160, which is formed to a bottomedcylindrical shape, and a cover body 161 which blocks the opening of thecase body 160, and the case body 160 is formed by bending a peripheralpart 160A of the case body 60 outwards. The cover body 161 is integrallyformed by including a disk part 161A which is formed to havesubstantially the same diameter as that of the opening of the case body160, a cylinder part 161B which is connected to the fringe of the diskpart 161A and is fitted into the internal peripheral surface of the casebody 160, and a flexed part 161C which is formed by bending outwards thefringe of the cylinder part 161B, the disk part 161A and the cylinderpart 161B enter into the case body 160, and the flexed part 161C abutsagainst and is fixed to the peripheral part 160A of the case body 160.Thereby, in the electric motor 110, one end (front end) of the case 111is caved inwards, and a fitting cavity 63, which the pump body 120 isfitted to in a pillbox manner, is formed.

A through hole 161D where the output shaft 112 penetrates and a recess161E which holds an outer ring of the bearing 162 that pivotallysupports the output shaft 112 are formed substantially in the center ofthe disk part 161A.

The pump body 120 includes, as shown in FIG. 7, a casing body 122 whichis fitted into the fitting cavity 163 which is formed at the front sideof the case 111 of the electric motor 110, a cylinder part 123 which ispress fitted in the casing body 122 and forms a cylinder chamber S, anda pump cover 124 which covers the casing body 122 from the front side.In this embodiment, a casing 131 of the vacuum pump 101 is formed byincluding the casing body 122, the cylinder part 123 and the pump cover124.

The casing body 122 uses, for example, metal materials such as aluminumwhose thermal conductivity is high, and as shown in FIG. 8, the shape ofthe casing body 122, when viewed from front, is formed to asubstantially rectangular shape which is longer in the up-down directionwith the above-mentioned rotation center X1 as an approximate center. Acommunicating hole 122A, which communicates with the cylinder chamber Swhich the casing body 122 is provided with, is formed in the upper partof the casing body 122, and an vacuum absorbing nipple(intake pipe) 130is press fitted to the communicating hole 122A. As shown in FIG. 7, thevacuum absorbing nipple 130 is a pipe which is bent to a rough L shape,and a pipe or tube for supplying underpressure air from an externalequipment (for example, a vacuum tank (not shown in the figure)) isconnected to one end 130A of the vacuum absorbing nipple 130. In thisembodiment, because the vacuum absorbing nipple 130 is press fitted intothe communicating hole 122A of the casing body 122, when a positionwhere the external equipment is arranged is determined beforehand as ina vehicle, the vacuum absorbing nipple 130 may be press fitted byturning the end 130A to the direction in which the external equipment isarranged so that with a simple configuration, the direction in which thepipe or tube for supplying underpressure air is drawn out can be setfreely.

A bore 122B around a central axis X2 which extends in the front-reardirection is formed in the casing body 122, and a cylinder part 23 whichis formed to a cylindrical shape is press fitted into the bore 122B. Thecentral axis X2 is parallel with the rotation center X1 of the outputshaft 112 of the above-mentioned electric motor 110, and as shown inFIG. 8, is offset to the upper left side relative to the rotation centerX1. In this configuration, the central axis X2 is offset so that theouter peripheral surface 127B of the rotor 127 to be described lateraround the rotation center X1 is adjacent to the internal peripheralsurface 123A of the cylinder part 123 that is formed around the centralaxis X2.

The cylinder part 123 is formed of metal material (in the presentembodiment, iron) which is the same as that of the rotor 127. With thisconfiguration, because the thermal expansion coefficients of thecylinder part 123 and the rotor 127 are the same, regardless oftemperature change of the cylinder part 123 and the rotor 127, thecontact of the outer peripheral surface 127B of the rotor 127 and theinternal peripheral surface 123A of the cylinder body 23 when the rotor127 is rotated can be prevented.

Furthermore, because the thermal expansion coefficients of the cylinderpart 123 and the rotor 127 are the same, the clearance between the sidesurface of the rotor 127 and the side plates 125 and 126 (to bedescribed later) which are arranged at the rear end and the front end ofthe cylinder part 123, respectively, can be stabilized.

Because the cylinder part 23 can be accommodated in the length range ofthe front-rear direction of the casing body 122 by press fitting thecylinder part 123 into the bore 122B which is formed in the casing body122, the cylinder part 123 is prevented from being protruded from thecasing body 122 and the casing body 122 can be downsized.

Furthermore, the casing body 122 is formed of material whose thermalconductivity is higher than that of the rotor 127.

Thereby, since the heat that is generated when the rotor 127 and vanes128 are rotationally driven can be transmitted to the casing body 122immediately, the heat from the casing body 122 can be dissipatedsufficiently.

Substantially, because aluminum has a thermal expansion coefficientbigger than that of iron, the press fitting amount of the cylinder part123 tends to be decreased when the temperature of the pump body 120becomes high. Therefore, in this structure, the opening (communicatinghole) 123B which is coupled to the communicating hole 122A of the casingbody 122 is formed in the cylinder part 123, and the other end (frontend) 130B of the vacuum absorbing nipple 130 is arranged to be engagedwith the opening 123B. Thus, even if the press fitting amount of thecylinder part 123 is decreased due to thermal expansion, because theother end 130B of the vacuum absorbing nipple 130 is engaged with theopening 123B of the cylinder part 123, the cylinder part 123 can beprevented from being rotated or falling out.

At the lower part of the casing body 122 and the cylinder part 123,discharging ports 122C and 123C, which penetrate the casing body 122 andthe cylinder part 123 and where the air compressed in the cylinderchamber S is exhausted, are provided.

Side plates 125 and 126 are disposed at the rear end and the front endof the cylinder part 123, respectively. The diameter of the side plates125 and 126 is set to be larger than the inside diameter of the internalperipheral surface 123A of the cylinder part 23. The side plates 125 and126 are pressed against the front end and the rear end of the cylinderpart 123, respectively, by being biased by gaskets 125A and 126A.Thereby, the sealed cylinder chamber S is formed inside the cylinderpart 123 except the opening 123B which is coupled to the vacuumabsorbing nipple 130 and the discharging ports 123C and 122C.

In the cylinder chamber S inside the cylinder part 123, the rotor 127 isdisposed. The rotor 127 is formed into a thick cylindrical shape, andthe output shaft 112 on which the above-mentioned spline part 112B isformed is fitted to the internal peripheral surface 127A of the rotor127. With this spline fitting configuration, the rotor 127 is rotatedintegrally with the output shaft 12. The length in the front-reardirection of the rotor 127 is set to be substantially equal to thelength of the cylinder part 123, namely, the distance between themutually opposed inside surfaces of the above-mentioned two pieces ofside plates 125 and 126. The outer diameter of the rotor 127 is set sothat, as shown in FIG. 8, the outer peripheral surface 27B of the rotor127 keeps a minute clearance from a part among the internal peripheralsurface 123A of the cylinder part 123 that is located at the lower rightside. Thereby, as shown in FIG. 8, a space of a crescent shape is formedbetween the outer peripheral surface 127B of the rotor 127 and theinternal peripheral surface 123A of the cylinder part 123.

The rotor 127 is provided with a plurality of (in this example, fivepieces) vanes 128 which partition the crescent space. The vane 128 isformed into a board shape, and the length in the front-rear direction isset to be substantially equal to the distance between the mutuallyopposed inside surfaces of the two pieces of side plates 125 and 126,like the rotor 127. These vanes 128 are disposed to be extendable fromguide grooves 127C which the rotor 127 is provided with. The vanes 128are protruded outwards along the guide grooves 127C by a centrifugalforce with the rotation of the rotor 127 so that the front ends of thevanes 28 abut with the internal peripheral surface 123A of the cylinderpart 123. Thereby, the above-mentioned crescent space is partitionedinto 5 compression chambers P surrounded by two pieces of mutuallyadjacent vanes 128 and 128, the outer peripheral surface 127B of therotor 127 and the internal peripheral surface 123A of the cylinder part123. These compression chambers P rotates in the same direction with therotation of the arrow R direction of the rotor 127 with the rotation ofthe output shaft 112, and the capacity of each of these compressionchambers P becomes bigger at positions near the opening 123B, andbecomes smaller at positions near the discharging port 123C. That is,with the rotation of the rotor 127 and the vanes 128, the air taken inone compression chamber P from the opening 23B rotates and is compressedwith the rotation of the rotor 127, and is discharged from theexhausting port 23C. In this configuration, the rotary compressingelements are formed by including the rotor 127 and the plurality ofvanes 128.

In this configuration, the cylinder part 123 is formed in the casingbody 122, as shown in FIG. 8, by offsetting the central axis X2 of thecylinder part 123 to the upper left side relative to the rotation centerX1. Therefore, the expansion chamber 133 communicating with thedischarging ports 123C and 122C is formed in the casing body 122 in adirection opposite to that the cylinder part 123 is offset. Theexpansion chamber 133 is formed into a crescent shape along the outerperipheral surface of the cylinder part 123, and the part near theexhausting port 123C and 122C swells further downward and communicateswith an exhausting port 124A formed in the pump cover 124. In thisconfiguration, because the cylinder part 123 is offset relative to therotation center X1 and formed in the casing body 122, the expansionchamber 133 communicating with the discharging ports 123C and 122C canbe formed in the casing body 122. Therefore, it is not necessary toprovide the expansion chamber 133 outside the casing body 122, thecasing body 122 can be downsized, and thus the vacuum pump 101 can bedownsized. The noise is reduced since the air exhausted from thedischarging ports 123C and 122 is led into the expansion chamber 133 andexpanded.

The pump cover 124 is arranged to the front side plate 126 via thegasket 126A, and is fixed to the casing body 122 with a bolt 134. On thefront of the casing body 122, as shown in FIG. 8, a sealing groove 122Dis formed by surrounding the cylinder part 123 and the expansion chamber133, and an annular sealing member 135 is arranged to the sealing groove122D. The exhausting port 124A is provided in the pump cover 124 at aposition corresponding to the expansion chamber 133. The exhausting port124A is intended to exhaust the air which flows into the expansionchamber 133 to the outside of the device (the outside of the vacuum pump101), and a check valve 129 for preventing the countercurrent of airfrom the outside of the device into the pump is attached to theexhausting port 124A.

FIG. 9 is a perspective view of the casing body 122 when viewed fromback.

As mentioned above, the vacuum pump 101 is formed by coupling theelectric motor 110 and the pump body 120, and the rotor 127 connected tothe output shaft 12 of the electric motor 110 and the vanes 128 slide inthe cylinder part 123 of the pump body 120. Therefore, it is importantto assemble the pump body 120 in accordance with the rotation center X1of the output shaft 112 of the electric motor 110.

Therefore, in this embodiment, as mentioned above, the fitting cavity163, which is centered on the rotation center X1 of the output shaft112, is formed at one end of the case 111 of the electric motor 110. Onthe other hand, on the back of the casing body 122, as shown in FIG. 9,a cylindrical fitting part 122F is integrally formed to be protrudedbackwards around the cylinder chamber S. The fitting part 122F is formedconcentrically with the rotation center X1 of the output shaft 112 ofthe electric motor 110, and is formed so that the outer edge of thefitting part 122F is engaged with the fitting cavity 163 of the electricmotor 110 in a pillbox manner.

Therefore, with this configuration, since only by fitting the fittingpart 122F of the casing body 122 into the fitting cavity 163 of theelectric motor 110, the central locations can be easily put together,the assembly of the electric motor 110 and the pump body 120 can beeasily performed. Further, on the back of the casing body 122, a sealinggroove 122E is formed around the fitting part 122F, and a circularsealing member 136 is arranged to the sealing groove 122E.

With this configuration, because the electric motor 110 and the pumpbody 120 can be fixed provisionally by engaging the electric motor 110and the pump body 120 in a pillbox manner, the casing body 122 and thecase 111 of the electric motor 110 can be collectively fixed with thebolt 134 for fixing the pump cover 124.

In particular, as shown in FIG. 110A, a female screw part 160A1 isprovided at the peripheral part 160A of the case body 160, and byengaging the bolt 134 threadedly with the female screw part 160A1, thepump cover 124, the casing body 122 and the case 111 of the electricmotor 110 are collectively fixed with one bolt 134. In this case, byforming the female screw part 160A1 to be thicker than the board of theperipheral part 160A, the pump cover 124, the casing body 122 and thecase 111 of the electric motor 110 can be fixed strongly.

As shown in FIG. 10B, while the female screw part 160A1 is formed bybeing protruded at the side of the casing body 122, it is also possibleto accommodate this female screw part 160A1 in a bore 160C1 which isformed in the flexed part 161C of the cover body 161. According to thisconfiguration, the female screw part 160A1 will not be protruded beyondthe surface of the vacuum pump 1 and exposed, and thus design-relatedimprovement can be achieved.

As mentioned above, according to the present embodiment, in the vacuumpump 101 including the rotor 127 and the vanes 128 in the casing, thecasing includes the casing body 122 formed of material whose thermalconductivity is higher than that of the rotor 27 or the vanes 128, andthe cylinder part 123 on which the rotor 127 and the vanes 128 which arepress fitted in the casing body 122 slide. Therefore, since the casing131 is formed by press fitting the cylinder part 123 in the casing body122, the casing 131 can be downsized. Because the casing body 122 isformed of material whose thermal conductivity is higher than that of therotor 127 and the vanes 128, since the heat that occurred when the rotor127 and the vanes 128 are rotationally driven can be transmitted to thecasing body 122 immediately, the heat from the casing body 122 can bedissipated sufficiently.

According to the present embodiment, the casing body 122 and thecylinder part 123 include the communicating hole 122A and the opening123B which communicate with the cylinder part 123 by penetrating throughthe casing body 122 and the cylinder part 123, respectively, and whilethe vacuum absorbing nipple 130 is press fitted into the communicatinghole 122A, the other end 130B of the vacuum absorbing nipple 130 isengaged with the opening 123B of the cylinder part 123. Therefore, forexample, when aluminum having a high thermal expansion coefficient isused for the casing body 122, and iron having a low thermal expansioncoefficient is used for the cylinder part 123, even if the press fittingamount of the cylinder part 123 is decreased due to thermal expansion,because the other end 130B of the vacuum absorbing nipple 130 is engagedwith the opening 123B of the cylinder part 123, the cylinder part 123can be prevented from being rotated or falling out.

According to the present embodiment, the cylinder part 123 is formed ofmaterial having a thermal expansion coefficient that is substantiallyequal to that of the rotor 127. Therefore, the clearance between theside surfaces of the rotor 127 and the side plates 125 and 126 can beprevented from being changed with temperature change, and the internalperipheral surface 123A of the cylinder body 23 and the outer peripheralsurface 127 of the rotor 127 can be prevented from being contacted withtemperature change.

According to the present embodiment, in the casing body 122, thecylinder part 123 is arranged at a position that is offset from therotation center X1 of the rotor 127, and the expansion chamber 133communicating with the cylinder part 123 is formed at the peripheralpart of the cylinder part 123 at the side of the rotation center X1.Therefore, it is not necessary to provide the expansion chamber 133outside the casing body 122, the casing body 122 can be downsized, andthus the vacuum pump 101 can be downsized.

The preferred embodiments for performing the present invention aredescribed as above, but the present invention is not limited to thepreviously described embodiments, and various modifications and changesare possible based on the technical thought of the present invention.For example, in this embodiment, the vane-type vacuum pump is used asthe vacuum pump 1, but if rotary compressing elements are included, forexample, a scroll type vacuum pump may be used.

FIG. 11 is a side partial sectional view of a vacuum pump (compressingdevice) 201 according to the embodiment of the invention to achieve thethird object. FIG. 12 is a figure of the vacuum pump 201 of FIG. 11 whenviewed from the front side of the vacuum pump 201 (the right side in thefigure above). However, FIG. 12 illustrates a state that those memberssuch as a pump cover 224 and a side plate 226 are removed in order toshow the configuration of a cylinder chamber S. In FIG. 12, a state thatan attaching member 240 is removed is shown. In the following, for theconvenience of description, the directions respectively indicated by thearrows in the upper parts of FIGS. 11 and 12 are the up, down, front,rear, right and left directions of the vacuum pump 201. The front-reardirection is an axial direction, and the right-left direction is anwidthwise direction.

The vacuum pump 201 shown in FIG. 11 is a rotary vane-type vacuum pump,and, for example, is used as a vacuum source of a brake boosting device(not shown in the figure) of an automobile or the like. In this case,the vacuum pump 201 is usually arranged in an engine room and isconnected with pipes to the brake boosting device through a vacuum tank(not shown in the figure). The use range of the vacuum pump 201 used forautomobiles or the like is, for example, −60 kPa to −80 kPa.

As shown in FIG. 11, the vacuum pump 201 includes an electric motor 210and a pump body 220 which is arranged to the electric motor 210, and theelectric motor 210 and the pump body 220 are fixed to and supported by avehicle body 250 of, for example, an automobile in an integrallyconnected state by an attaching member 240.

The attaching member 240 includes an attaching plate 241 which isprovided with a rectangular projecting slot 241A that extends in thewidthwise direction of the pump body 220, and vibration proof rubbers242 and 242 which are fixed to the front end and the rear end of theattaching plate 241, respectively. These vibration proof rubbers 242 and242 are held by being fitted into bores formed on the vehicle body. Theattaching plate 241 is fixed with a bolt 243 onto the bottom surface ofthe pump body 220 at the projecting slot 241A.

The electric motor 210 has an output shaft 212 which extendssubstantially from the center of one end (front end) of a case 211,which is formed into a substantially cylindrical shape, towards the sideof the pump body 220 (front side). The output shaft 212 rotates around arotation center X1 that extends in the front-rear direction. A splinepart 212B, which is fitted into a rotor 227 of the pump body 220 to bedescribed below and turns and stops the rotor 227, is formed at thefront end part 212A of the output shaft 212. By providing a key on theoutside surface of the output shaft 212, the skidding of the rotor 227can be prevented.

When a power supply (not shown in the figure) is switched ON, the outputshaft 212 of the electric motor 210 rotates in an arrow R direction(counterclockwise direction) in FIG. 12, and thereby the rotor 227 isrotated in the same direction (arrow R direction) around the rotationcenter X1.

The case 211 includes a case body 260, which is formed to a bottomedcylindrical shape, and a cover body 261 which blocks the opening of thecase body 260, and the case body 260 is formed by bending a peripheralpart 260A of the case body 260 outwards. The cover body 261 isintegrally formed by including a disk part 261A which is formed to havesubstantially the same diameter as that of the opening of the case body260, a cylinder part 261B which is connected to the fringe of the diskpart 261A and is fitted into the internal peripheral surface of the casebody 260, and a flexed part 261C which is formed by bending outwards thefringe of the cylinder part 261B, the disk part 261A and the cylinderpart 261B enter into the case body 260, and the flexed part 261C abutsagainst and is fixed to the peripheral part 260A of the case body 260.Thereby, in the electric motor 210, one end (front end) of the case 211is caved inwards, and a fitting cavity 263, which the pump body 220 isfitted to in a pillbox manner, is formed.

A through hole 261D where the output shaft 212 penetrates and a recess61E which holds an outer ring of the bearing 62 that pivotally supportsthe output shaft 212 are formed substantially in the center of the diskpart 261A.

The pump body 220 includes, as shown in FIG. 11, a casing body 222 whichis fitted into the fitting cavity 263 which is formed at the front sideof the case 211 of the electric motor 210, a cylinder part 223 which ispress fitted in the casing body 222 and forms a cylinder chamber S, anda pump cover 224 which covers the casing body 222 from the front side.In this embodiment, a casing 231 of the vacuum pump 201 is formed byincluding the casing body 222, the cylinder part 223 and the pump cover224.

The casing body 222 uses, for example, metal materials such as aluminumwhose thermal conductivity is high, and as shown in FIG. 12, the shapeof the casing body 222, when viewed from front, is formed to asubstantially rectangular shape which is longer in the up-down directionwith the above-mentioned rotation center X1 as an approximate center. Acommunicating hole 222A, which communicates with the cylinder chamber Swhich the casing body 222 is provided with, is formed in the upper partof the casing body 222, and a vacuum absorbing nipple 230 is pressfitted to the communicating hole 222A. As shown in FIG. 11, the vacuumabsorbing nipple 230 is a pipe which is bent to a rough L shape, and apipe or tube for supplying underpressure air from an external equipment(for example, a vacuum tank (not shown in the figure)) is connected toone end 230A of the vacuum absorbing nipple 230. In this embodiment,because the vacuum absorbing nipple 230 is press fitted into thecommunicating hole 222A of the casing body 222, when a position wherethe external equipment is arranged is determined beforehand as in avehicle, the vacuum absorbing nipple 230 may be press fitted by turningthe end 230A to the direction in which the external equipment isarranged so that with a simple configuration, the direction in which thepipe or tube for supplying underpressure air is drawn out can be setfreely.

A bore 222B around a central axis X2 which extends in the front-reardirection is formed in the casing body 222, and a cylinder part 223which is formed to a cylindrical shape is press fitted into the bore222B. The central axis X2 is parallel with the rotation center X1 of theoutput shaft 212 of the above-mentioned electric motor 210, and as shownin FIG. 12, is offset to the upper left side relative to the rotationcenter X1. In this configuration, the central axis X2 is offset so thatthe outer peripheral surface 227B of the rotor 227 to be described lateraround the rotation center X1 is adjacent to the internal peripheralsurface 223A of the cylinder part 223 that is formed around the centralaxis X2.

The cylinder part 223 is formed of metal material (in the presentembodiment, iron) which is the same as that of the rotor 227. With thisconfiguration, because the thermal expansion coefficients of thecylinder part 223 and the rotor 227 are the same, regardless oftemperature change of the cylinder part 223 and the rotor 227, thecontact of the outer peripheral surface 227B of the rotor 227 and theinternal peripheral surface 223A of the cylinder part 223 when the rotor227 is rotated can be prevented.

Because the cylinder part 223 can be accommodated in the length range ofthe front-rear direction of the casing body 222 by press fitting thecylinder part 223 into the bore 222B which is formed in the casing body222, the cylinder part 223 is prevented from being protruded from thecasing body 222 and the casing body 222 can be downsized.

Furthermore, the casing body 222 is formed of material whose thermalconductivity is higher than that of the rotor 227. Thereby, since theheat that is generated when the rotor 227 and vanes 228 are rotationallydriven can be transmitted to the casing body 222 immediately, the heatfrom the casing body 222 can be dissipated sufficiently.

An opening 223B which is coupled with the communicating hole 222A of theabove described casing body 222 and the cylinder chamber S is formed atthe cylinder part 223, and the air passing through the vacuum absorbingnipple 230 is supplied to the cylinder chamber S through thecommunicating hole 222A and the opening 223B. Therefore, in thisembodiment, an intake path 232 is formed by including the vacuumabsorbing nipple 230, the communicating hole 222A of the casing body 222and the opening 223B of the cylinder part 223. At the lower part of thecasing body 222 and the cylinder part 223, discharging ports 222C and223C, which penetrate the casing body 222 and the cylinder part 223 andwhere the air compressed in the cylinder chamber S is exhausted, areprovided.

Side plates 225 and 226 are disposed at the rear end and the front endof the cylinder part 223, respectively. The diameter of the side plates225 and 226 is set to be larger than the inside diameter of the internalperipheral surface 223A of the cylinder part 223. The side plates 225and 226 are pressed against the front end and the rear end of thecylinder part 223, respectively, by being biased by gaskets 225A and226A. Thereby, the sealed cylinder chamber S is formed inside thecylinder part 223 except the opening 223B which is coupled to the vacuumabsorbing nipple 230 and the discharging ports 223C and 222C.

In the cylinder chamber S inside the cylinder part 223, the rotor 227 isdisposed. The rotor 227 is formed into a thick cylindrical shape, andthe output shaft 212 on which the above-mentioned spline part 2128 isformed is fitted to the internal peripheral surface 227A of the rotor127. With this spline fitting configuration, the rotor 227 is rotatedintegrally with the output shaft 212. The length in the front-reardirection of the rotor 227 is set to be substantially equal to thelength of the cylinder part 223, namely, the distance between themutually opposed inside surfaces of the above-mentioned two pieces ofside plates 225 and 226. The outer diameter of the rotor 227 is set sothat, as shown in FIG. 12, the outer peripheral surface 227B of therotor 227 keeps a minute clearance from a part among the internalperipheral surface 223A of the cylinder part 223 that is located at thelower right side. Thereby, as shown in FIG. 12, a space of a crescentshape is formed between the outer peripheral surface 227B of the rotor227 and the internal peripheral surface 223A of the cylinder part 223.

The rotor 227 is provided with a plurality of (in this example, fivepieces) vanes 228 which partition the crescent space. The vane 228 isformed into a board shape, and the length in the front-rear direction isset to be substantially equal to the distance between the mutuallyopposed inside surfaces of the two pieces of side plates 225 and 226,like the rotor 227. These vanes 228 are disposed to be extendable fromguide grooves 227C which the rotor 227 is provided with. The vanes 228are protruded outwards along the guide grooves 227C by a centrifugalforce with the rotation of the rotor 227 so that the front ends of thevanes 28 abut with the internal peripheral surface 223A of the cylinderpart 223. Thereby, the above-mentioned crescent space is partitionedinto 5 compression chambers P surrounded by two pieces of mutuallyadjacent vanes 228 and 228, the outer peripheral surface 227B of therotor 227 and the internal peripheral surface 223A of the cylinder part223. These compression chambers P rotates in the same direction with therotation of the arrow R direction of the rotor 227 with the rotation ofthe output shaft 212, and the capacity of each of these compressionchambers P becomes bigger at positions near the opening 223B, andbecomes smaller at positions near the discharging port 223C. That is,with the rotation of the rotor 227 and the vanes 228, the air taken inone compression chamber P from the opening 223B rotates and iscompressed with the rotation of the rotor 227, and is discharged fromthe discharging port 223C. In this configuration, the rotary compressingelements are formed by including the rotor 227 and the plurality ofvanes 228.

In this configuration, the cylinder part 223 is formed in the casingbody 222, as shown in FIG. 12, by offsetting the central axis X2 of thecylinder part 223 to the upper left side relative to the rotation centerX1. Therefore, in the casing body 222, a big space in the directionopposite to that the cylinder part 223 is offset can be secured, and anexpansion chamber 233 that communicates with the discharging ports 223Cand 222C and a resonance chamber 234 which is aligned with the expansionchamber 233 at the peripheral part of the cylinder part 223 are formedin this space. The expansion chamber 233 and the resonance chamber 234are separated by a rib 235 formed integrally with the casing body 222,and as shown in FIG. 13, an orifice 235A which connects the expansionchamber 233 and the resonance chamber (resonator) 234 is formed in therib 235.

The expansion chamber 233 is formed as a big closed space below thecylinder part 223, and communicates with the exhausting port 224A whichis formed in the pump cover 224. After the compressed air which flowsinto the expansion chamber 233 is expanded and scattered in theexpansion chamber 233, the air hits the wall of the expansion chamber233 and is reflected diffusely. Thereby, since the sound energy of thecompressed air is attenuated, the noise and the vibration in theair-exhausting can be reduced. In the embodiment, an exhausting path 237is formed by including the discharging ports 222C and 223C, which areformed in the casing body 222 and the cylinder part 223, respectively,the expansion chamber 233 and the exhausting port 224A.

With the vane-type vacuum pump 201, because air is compressed when therotor 227 and the vanes 228 are rotated in the cylinder chamber S, thecompressed air is discharged intermittently from the discharging ports223C and 222C of the cylinder chamber S to the expansion chamber 233.Therefore, since pressure pulsation occurs at a constant basic frequencyin the discharging ports 223C and 222C of the cylinder chamber S, thenoise and vibration due to this pressure pulsation may occur.

Therefore, in this embodiment, the Helmholtz-type resonance chamber 234,which is branched from the exhausting path 237, is connected to theexpansion chamber 233. The resonance chamber 234 is formed to produceresonance that counteracts the pressure pulsation of the compressed airflowing through the exhausting path 237, and inhibits the noise andvibration due to the pressure pulsation.

The resonance chamber 234 is designed to produce a resonance frequencycorresponding to the above described basic frequency of the pressurepulsation of air, and in particular, this resonance frequency isdetermined by the length and the area of the orifice 235A for connectingwith the expansion chamber 233 and the capacity of the resonance chamber234.

According to this configuration, by connecting the resonance chamber 234to the expansion chamber 233 through the orifice 235A, the sound energyof the air expanded in the expansion chamber 233 is vibrated by an airspring in the orifice 235A and the resonance chamber 234 and attenuated.Therefore, the pressure pulsation of the air discharged with therotation of the rotor 227 and the vanes 228 can be reduced, and thenoise and vibration in the air-exhausting can be further reduced.

Furthermore, in this embodiment, by arranging the cylinder part 223 tobe offset from the rotation center X1 of the rotor 227, a big space atthe peripheral part of the cylinder part 223 at the side of the abovementioned rotation center X1 can be ensured in the casing body 222.Therefore, because the expansion chamber 233 and the resonance chamber234 can be integrally formed in the casing body 222 by adjacentlyproviding the expansion chamber 233 and the resonance chamber 234 inthis space, it is not necessary to provide the expansion chamber 233 andthe resonance chamber 234 outside the casing body 222, the casing body222 can be downsized and thus the vacuum pump 201 can be downsized.

Further, in the casing body 222, an intake side expansion chamber 238 isformed at the peripheral part of the cylinder part 223 at the side ofoffsetting the cylinder part 223. The intake side expansion chamber 238is provided in the intake path 232 connecting the above described vacuumabsorbing nipple 230 and the cylinder chamber S, and in the presentembodiment, the intake side expansion chamber 238 is separatedrespectively from the expansion chamber 233 and the resonance chamber234 by ribs 239 and 236 that are integrally provided in the casing body222.

According to this configuration, since the air flowing through theintake path 232 is expanded and scattered in the intake side expansionchamber 238 and reflected diffusely by hitting the wall of the intakeside expansion chamber 238, the sound energy is attenuated. Thus, thenoise and the vibration in the air intake can be reduced as well asthose in the air-exhausting.

In the intake side expansion chamber 238, for example, a desiccatingagent 265 such as silica gel or zeolite is arranged. The desiccatingagent 265 is formed by adhering silica gel or zeolite grains to such asize that the discharging ports 223C and 222C cannot be passed, andremoves the water of the air flowing in the intake side expansionchamber 238. Therefore, because the air in which water is removed by thedesiccating agent 265 flows into the cylinder chamber S, dewcondensation in the cylinder chamber S is prevented and the corrosion ofthe rotor 227 and the cylinder part 223 and the freeze in the cylinderchamber S due to the dew condensation can be prevented.

Because the intake side expansion chamber 238 is formed at theperipheral part of the cylinder chamber S, the vacuum absorbing nipple230 communicates with the cylinder chamber S through the intake sideexpansion chamber 238. Therefore, the vacuum absorbing nipple 230 can beprovided in any places in the range where the intake side expansionchamber 238 extends, and the attaching position of the vacuum absorbingnipple 230 can be changed depending on the position where the vacuumpump 201 is arranged in the vehicle.

In this embodiment, because in the casing body 222, the expansionchamber 233, the resonance chamber 234 and the intake side expansionchamber 238 are formed at the peripheral part of the cylinder part 223,the expansion chambers 233, the resonance chamber 234 and the intakeside expansion chamber 238 can be collectively well arranged in thecasing body 222. Therefore, it is not necessary to provide the intakeside expansion chamber 238 outside the casing body 222, the casing body222 can be downsized, and thus the vacuum pump 201 can be downsized. Inthis embodiment, the expansion chamber 233, the resonance chamber 234and the intake side expansion chamber 238 are arranged at the peripheralpart of the cylinder part 223, and the expansion chambers 233, theresonance chamber 234 and the intake side expansion chamber 238 areseparated from each other by the ribs 235, 236 and 239. Therefore, bychanging the positions of these ribs 235, 236 and 239, the size of eachof the expansion chamber 233, the resonance chamber 234 and the intakeside expansion chamber 238 can be changed. For example, after the sizeof the resonance chamber 234 is determined, the sizes of the expansionchamber 233 and the intake side expansion chamber 238 can beappropriately set.

The pump cover 224 is arranged to the front side plate 226 via a gasket226A, and is fixed to the casing body 222 with a bolt 266. On the frontof the casing body 222, as shown in FIG. 12, a sealing groove 222D isformed by surrounding the cylinder part 223 and the expansion chamber233, and an annular sealing member 267 is arranged to the sealing groove222D. The exhausting port 224A is provided in the pump cover 224 at aposition corresponding to the expansion chamber 233. The exhausting port224A is intended to exhaust the air which flows into the expansionchamber 233 to the outside of the device (the outside of the vacuum pump201), and a check valve 229 for preventing the countercurrent of airfrom the outside of the device into the pump is attached to theexhausting port 224A.

As described above, according to the present embodiment, the casing 231includes the casing body 222 in which the cylinder chamber S, in whichthe rotor 227 and the vanes 228 slide, is formed, the exhausting path237 that connects the cylinder chamber S and the exhausting port 224A,and the expansion chamber 233 formed in the exhausting path 237, and theexpansion chamber 233 is provided at the peripheral part of the cylinderchamber S in the casing body 222. Therefore, since the compressed airflowing through the exhausting path 237 is expanded and scattered in theexpansion chamber 233 and reflected diffusely by hitting the wall of theexpansion chamber 233, the sound energy of the air is attenuated, andthereby the noise and the vibration when the air is exhausted from theexhausting port 224A to the outside of the device can be reduced.Furthermore, because the expansion chamber 233 is provided at theperipheral part of the cylinder chamber S in the casing body 222, thecylinder chamber S and the expansion chamber 233 can be formedintegrally in the casing body 222 and the upsizing of the vacuum pump201 can be inhibited.

According to the present embodiment, the Helmholtz-type resonancechamber 234 which is branched from the exhausting path 237 is connectedto the expansion chamber 233 through the orifice 235A. Thus, the soundenergy of the air expanded in the expansion chamber 233 is vibrated bythe air spring in the orifice 235A and the resonance chamber 234 and isattenuated. Therefore, the pressure pulsation of the air discharged fromthe cylinder chamber S can be reduced, and the noise and the vibrationin the air-exhausting can be further reduced.

According to the present embodiment, because the cylinder chamber S isprovided at the position that is offset from the rotation center X1 ofthe rotor 227 and the vanes 228 in the casing body 222, a big space atthe peripheral part of the cylinder chamber at the side of the rotationcenter can be secured in the casing body. Therefore, by adjacentlyproviding the expansion chamber and the resonance chamber in this space,it is not necessary to provide the expansion chamber and the resonancechamber outside the casing body, the casing body can be downsized andthus the compressing device can be downsized.

According to the present embodiment, the intake path 232 which leads airto the cylinder chamber S is included and the intake side expansionchamber 238 that expands the air flowing in the intake path 232 isprovided in the intake path 232. Therefore, because the air taken in thecylinder chamber S is expanded and scattered in the intake sideexpansion chamber 238 so that the sound energy is attenuated, the noiseand the vibration in the air intake can be reduced as well as those inthe air-exhausting.

According to the present embodiment, the intake side expansion chamber238 is formed at the peripheral part of the cylinder chamber S in thecasing body 222 along with the expansion chamber 233. Therefore, byproviding the expansion chamber 233 and the intake side expansionchamber 238 at the peripheral part of the cylinder chamber S, thecylinder chamber S, the expansion chamber 233 and the intake sideexpansion chamber 238 can be formed integrally in the casing body 222and the upsizing of the vacuum pump 201 can be inhibited.

According to the present embodiment, the desiccating agent 265 isaccommodated in the intake side expansion chamber 238. Therefore, byremoving the water in the air flowing into the cylinder chamber Sthrough the intake path 232, dry air can be supplied to the cylinderchamber S and dew condensation at the cylinder chamber S, the rotor 227and the vanes 228 can be prevented. Therefore, corrosion and freeze ofthe rotor 227 can be prevented and the life span of the vacuum pump 201can be extended.

Then, another embodiment is described.

FIG. 14 is a side partial sectional view of a vacuum pump 200 accordingto the embodiment.

This embodiment differs in configuration from the above mentionedembodiment in that a resonance chamber is formed in the case 211 of theelectric motor 210. The same components as the above components aregiven the same symbols and their description is omitted.

As shown in FIG. 14, the vacuum pump 200 includes a first orifice 233Awhich is provided at the expansion chamber 233 which is formed in thecasing body 222, and a second orifice 264 which is formed in the coverbody 261 of the case 211 and is connected to the first orifice 233A, andthrough the first orifice 233A and the second orifice 264, the expansionchamber 233 and the inside of the case 211 are connected. In thisembodiment, a space 211A in the case 211 functions as a Helmholtz-typeresonance chamber.

This embodiment is useful, for example, when the outer diameter of thepump body 220 is small and a resonance chamber cannot be formed at theperipheral part of the cylinder part 223. Because the case 211 as aHelmholtz-type resonance chamber which is branched from the exhaustingpath 237 is connected to the expansion chamber 233 through the firstorifice 233A and the second orifice 264, the sound energy of the airexpanded in the expansion chamber 233 is vibrated by the air spring inthe first orifice 233A, the second orifice 264 and the case 211 and isattenuated. Therefore, the pressure pulsation of the air discharged fromthe cylinder chamber S can be reduced, and the noise and the vibrationin the air-exhausting can be further reduced.

FIG. 15 is a side partial sectional view of a vacuum pump 202 accordingto another embodiment.

This embodiment differs in configuration from the above mentionedembodiment in that an intake side expansion chamber is formed in thecase 211 of the electric motor 210. The same components as the abovecomponents are given the same symbols and their description is omitted.

With this configuration, in the vacuum pump 202, an intake port 260A1 isformed in the case body 260 which forms the case 211 of the electricmotor 210, and the above described vacuum absorbing nipple 280 isconnected to the intake port 260A1. A first communicating hole 271extending axially and a second communicating hole 272 which communicateswith the first communicating hole 271 and the opening 223B of thecylinder part 223 are formed in the casing body 222, and a communicatinghole 268 communicating with the first communicating hole 271 is formedin the cover body 261. Thereby, the space 211A in the case 211communicates with the cylinder chamber S through the communicating hole268, the first communicating hole 271, the second communicating hole 272and the opening 223B, and an intake path 282 is formed by including thecommunicating hole 268, the first communicating hole 271, the secondcommunicating hole 272 and the opening 223B.

Therefore, in this embodiment, because the space 211A in the case 211 isprovided in the intake path 282, the air taken in the cylinder chamber Sis attenuated by being expanded and scattered in the space 211A. Thus,the noise and the vibration in the air intake can be reduced as well asthose in the air-exhausting. Furthermore, because the air flow thatflows into the space in the case 211 through the vacuum absorbing nipple280 cools the coil or the commutator (not shown in the figure) that isaccommodated in the case 211, extra cooling devices are not necessaryeven if the case 211 is arranged in a bad environment such as an engineroom, and the number of components can be reduced.

The preferred embodiments for performing the present invention aredescribed as above, but the present invention is not limited to thepreviously described embodiments, and various modifications and changesare possible based on the technical thought of the present invention.For example, in this embodiment, the vane-type vacuum pump is used asthe compressing device, but if rotary compressing elements are included,a scroll type vacuum pump may be used. In the above describedembodiment, it is described that the resonance chamber 234 (or the space211A in the case 211) are combined together with the expansion chamber233 at the exhausting side, but the resonance chamber may be combinedtogether with the intake side expansion chamber 238 (or the space 211Ain the case 211).

The resonance chamber of FIG. 14 may be combined with the abovedescribed vacuum pump 201 of FIG. 11. That is to say, besides that theexpansion chamber 233 and the resonance chamber 234 are provided at theperipheral part of the cylinder part 223 of the casing body 222, bycommunicating the expansion chamber 233 and the case 211 of the electricmotor 210 through the first orifice 233A and second orifice 264, aresonance chamber other than the resonance chamber 234 may be formed inthe case 211. According to this configuration, by changing the crosssection areas and lengths of the first orifice 233A and the secondorifice 264 or the volume inside the case 211 appropriately, thepressure pulsation of a different basic frequency can be correspondedto.

FIG. 16 is a side partial sectional view of a vacuum pump 301 accordingto the first embodiment of the invention to achieve the fourth object.FIG. 17 is a figure of the vacuum pump 301 of FIG. 16 when viewed fromthe front side of the vacuum pump 301 (the right side in the figureabove). However, FIG. 17 illustrates a state that those members such asa pump cover 324 and a side plate 326 are removed in order to show theconfiguration of a cylinder chamber S. In FIG. 17, a state that anattaching member 340 is removed is shown. In the following, for theconvenience of description, the directions respectively indicated by thearrows in the upper parts of FIGS. 16 and 17 are the up, down, front,rear, right and left directions of the vacuum pump 301. The front-reardirection is an axial direction, and the right-left direction is awidthwise direction.

The vacuum pump 301 shown in FIG. 16 is a rotary vane-type vacuum pump,and is used as a vacuum source of a brake boosting device (not shown inthe figure) of an automobile or the like. In this case, the vacuum pump301 is usually arranged in an engine room and is connected with pipes tothe brake boosting device through a vacuum tank (not shown in thefigure). The use range of the vacuum pump 301 used for automobiles orthe like is, for example, −60 kPa to −80 kPa.

As shown in FIG. 16, the vacuum pump 301 includes an electric motor 310and a pump body 320 which is operated by using the electric motor 310 asa driving source, and the electric motor 310 and the pump body 320 arefixed to and supported by a vehicle body 350 of, for example, anautomobile in an integrally connected state by an attaching member 340.

The attaching member 340 includes an attaching plate 341 which isprovided with a rectangular projecting slot 341A that extends in thewidthwise direction of the pump body 320, and vibration proof rubbers342 and 342 which are fixed to the front end and the rear end of theattaching plate 341, respectively. The attaching plate 341 is connectedto the bottom surface of the pump body 320 with a bolt 343 that passesthrough the projecting slot 341A, and these vibration proof rubbers 342and 342 are held by being fitted into bores formed at the side of thevehicle body 350.

The electric motor 310 has an output shaft 312 which is protrudedsubstantially from the center of one end (front end) of a case 311,which is formed into a substantially cylindrical shape, towards thefront side. The output shaft 312 functions as a driving shaft fordriving the pump body 320, and the output shaft 12 rotates around arotation center X1 extending in the front-rear direction. A front endpart 312A of the output shaft 312 is formed to a spline shaft and isengaged with a shaft hole 327A where the rotor 327 of the pump body 320is penetrated in the axial direction, so that the output shaft 312 andthe rotor 327 are connected to be integrally rotatable. Instead of thatthe output shaft 312 and the rotor 327 are spline coupled, the outputshaft 312 and the rotor 327 may be coupled through a key.

When a power supply (not shown in the figure) is switched ON, the outputshaft 312 of the electric motor 310 rotates in an arrow R direction(counterclockwise direction) in FIG. 17, and thereby the rotor 327 isrotated in the same direction (arrow R direction) around the rotationcenter X1.

The case 311 includes a case body 360, which is formed to a bottomedcylindrical shape, and a cover body 361 which blocks the opening of thecase body 360, and the case body 360 is formed by bending a peripheralpart 360A of the case body 60 outwards. The cover body 361 is integrallyformed by including a disk part 361A which is formed to havesubstantially the same diameter as that of the opening of the case body360, a cylinder part 361B which is connected to the fringe of the diskpart 361A and is fitted into the internal peripheral surface of the casebody 360, and a flexed part 361C which is formed by bending outwards thefringe of the cylinder part 361B, the disk part 361A and the cylinderpart 361B enter into the case body 360, and the flexed part 361C abutsagainst and is fixed to the peripheral part 360A of the case body 360.Thereby, in the electric motor 310, one end (front end) of the case 311is caved inwards, and a fitting cavity 363, which the pump body 320 isfitted to in a pillbox manner, is formed. A through hole 361D where theoutput shaft 312 penetrates and a recess 361E which holds an outer ringof the bearing (shaft bearing) 362 that pivotally supports the outputshaft 312 are formed substantially in the center of the disk part 361A.

The pump body 320 includes, as shown in FIG. 16, a casing body 322 whichis fitted into the fitting cavity 363 which is formed at the front sideof the case 311 of the electric motor 310, a cylinder part 323 which ispress fitted in the casing body 322 and forms a cylinder chamber S, anda pump cover 324 which covers the casing body 322 from the front side.In this embodiment, a casing 331 of the vacuum pump 301 is formed byincluding the casing body 322, the cylinder part 323 and the pump cover324.

The casing body 322 uses metal materials such as aluminum whose thermalconductivity is high, and as shown in FIG. 17, the shape of the casingbody 322, when viewed from front, is formed to a substantiallyrectangular shape which is longer in the up-down direction with theabove-mentioned rotation center X1 as an approximate center. Acommunicating hole 322A, which communicates with the cylinder chamber Swhich the casing body 322 is provided with, is formed in the upper partof the casing body 322, and an vacuum absorbing nipple(intake pipe) 330is press fitted to the communicating hole 322A.

As shown in FIG. 16, the vacuum absorbing nipple 330 is a pipe which isbent to a rough L shape, and a pipe or tube for supplying underpressureair from an external equipment (for example, a vacuum tank (not shown inthe figure)) is connected to one end 330A of the vacuum absorbing nipple330. In this embodiment, because the vacuum absorbing nipple 330 ispress fitted into the communicating hole 322A of the casing body 322,when a position where the external equipment is arranged is determinedbeforehand as in a vehicle, the vacuum absorbing nipple 330 may be pressfitted by turning the end 330A to the direction in which the externalequipment is arranged so that with a simple configuration, the directionin which the pipe or tube for supplying underpressure air is drawn outcan be set freely.

A bore 322B around a central axis X2 which extends in the front-reardirection is formed in the casing body 322, and a cylinder part 323which is formed to a cylindrical shape is press fitted into the bore322B. The central axis X2 is parallel with the rotation center X1 of theoutput shaft 312 of the above-mentioned electric motor 310, and as shownin FIG. 17, is offset to the upper left side relative to the rotationcenter X1. In the embodiment, the central axis X2 is offset so that theouter peripheral surface 327B of the rotor 327 around the rotationcenter X1 keeps a minute clearance from the internal peripheral surface323A of the cylinder part 323 that is formed to a circular surfacearound the central axis X2.

In FIG. 16, a symbol 334 is a bolt for fixing the pump cover 324 to thecasing body 322, a symbol 335 is a sealing member for blocking a gapbetween the casing body 322 and the pump cover 324, and a symbol 322D isa sealing groove where the sealing member 335 is installed. Further, asymbol 336 is a sealing member for blocking a gap between the casingbody 322 and the cover body 361, and a symbol 322E is a sealing groovewhere the sealing member 336 is installed.

The cylinder part 323 is formed of metal material (in the presentembodiment, iron) which is the same as that of the rotor 327. With thisconfiguration, because the thermal expansion coefficients of thecylinder part 323 and the rotor 327 are the same, regardless oftemperature change of the cylinder part 323 and the rotor 327, thecontact of the outer peripheral surface 327B of the rotor 327 and theinternal peripheral surface 323A of the cylinder part 323 when the rotor327 is rotated can be prevented. The cylinder part 323 and the rotor 327may use different materials as long as they are metal materials thathave substantially the same thermal expansion coefficient.

Because the cylinder part 323 can be accommodated in the length range ofthe front-rear direction of the casing body 322 by press fitting thecylinder part 323 into the bore 322B which is formed in the casing body322, the cylinder part 323 is prevented from being protruded from thecasing body 322 and the casing body 322 can be downsized.

Furthermore, the casing body 322 is formed of material whose thermalconductivity is higher than that of the rotor 327. Thereby, since theheat that is generated when the rotor 327 and vanes 328 are rotationallydriven can be transmitted to the casing body 322 immediately, the heatfrom the casing body 322 can be dissipated sufficiently.

Substantially, because aluminum has a thermal expansion coefficientbigger than that of iron, the press fitting amount of the cylinder part323 tends to be decreased when the temperature of the pump body 320becomes high. Therefore, in this structure, the opening (communicatinghole) 323B which is coupled to the communicating hole 322A of the casingbody 322 is formed in the cylinder part 323, and the other end (frontend) 330B of the vacuum absorbing nipple 330 is arranged to be engagedwith the opening 323B. Thus, even if the press fitting amount of thecylinder part 323 is decreased due to thermal expansion, because theother end 330B of the vacuum absorbing nipple 330 is engaged with theopening 323B of the cylinder part 323, the cylinder part 323 can beprevented from being rotated or falling out.

At the lower part of the casing body 322 and the cylinder part 323,discharging ports 322C and 323C, which penetrate the casing body 322 andthe cylinder part 323 and where the air compressed in the cylinderchamber S is exhausted, are provided.

Side plates 325 and 326 are disposed at the rear end and the front endof the cylinder part 323, respectively. The diameter of the side plates325 and 326 is set to be larger than the inside diameter of the internalperipheral surface 323A of the cylinder part 323. The side plates 325and 326 are pressed against the front end and the rear end of thecylinder part 323, respectively, by being biased by gaskets 325A and326A. Thereby, the sealed cylinder chamber S is formed inside thecylinder part 323 except the opening 323B which is coupled to the vacuumabsorbing nipple 330 and the discharging ports 323C and 322C.

In the cylinder chamber S, the rotor 327 is disposed. Because the vacuumpump 301 of the present embodiment is a vane-type pump, the rotor 327 isformed into a vane rotor having guide grooves 327C which are a pluralityof (five pieces) vane slits that accommodate a plurality of (in thepresent embodiment, five pieces) vanes 328 to be extendablesubstantially in the radial direction.

The rotor 327 has a cylindrical column shape which extends along therotation center X1 of the electric motor 310, and has an axial bore 327Athrough which the output shaft 312 which is a driving shaft of the pumpbody 320 is inserted. Meanwhile, at positions away from the axial bore327A in the radical direction, a plurality of guide grooves 327C areprovided around the axial bore 327A by being spaced in the peripheraldirection with an equal angular interval.

A spline groove, which is engaged with the spline shaft that is providedat the front end part 312A of the output shaft 312, is formed at theaxial bore 327A, and the rotor 327 and the output shaft 312 is adaptedto be spline connected.

The length in the front-rear direction of the rotor 327 is set to besubstantially equal to the length of the cylinder chamber S of thecylinder part 323, namely, the distance between the mutually opposedinside surfaces of the above-mentioned two pieces of side plates 325 and326, and the space between the rotor 327 and the side plates 325 and 326are substantially blocked.

The radius of the rotor 327 is set to the shortest distance between therotation center X1 and the internal peripheral surface 323A of thecylinder part 323, as shown in FIG. 17, and the outer peripheral surface327B of the rotor 327 is set to roughly contact a part of the internalperipheral surface 323A of the cylinder part 323 (a part located at thelower right side). Thereby, as shown in FIG. 17, a space of a crescentshape is formed between the outer peripheral surface 327B of the rotor327 and the internal peripheral surface 323A of the cylinder part 323.

The plurality of vanes 328 are partitioning members that partition thecrescent space, and the vanes 328 are formed into the same shape. Thevanes 328 are extended in the front-rear direction of the rotor 327 andset be substantially equal to the length of the cylinder chamber S ofthe cylinder part 323, namely, the distance between the mutually opposedinside surfaces of the above-mentioned two pieces of side plates 325 and326, and the space between the vanes 328 and the side plates 325 and 326are substantially blocked. The above mentioned crescent shape betweenthe cylinder chamber S and the rotor 327 is partitioned by the vanes 328into a plurality of (in the present embodiment, five) chambers.

These vanes 328 are made of carbon which is a light weight slidingmaterial superior in a sliding property, and are formed to be lighterthan those using a metal complex as other sliding materials. In thisembodiment, the rotary compressing elements are formed by including therotor 327 and the plurality of vanes 328.

FIG. 18A is a figure which shows a side surface of the rotor 327 withthe neighboring configuration, and FIG. 18B shows a B-B section of FIG.18A.

As shown in FIGS. 17 and 18A, the deepest parts 327D of the guidegrooves 327C are offset to positions apart from the rotation center X1of the rotor 327, and the guide grooves 327 extend outwards in theradial direction so that a contact angle 6A (refer to FIG. 18A) of thevanes 328 moving along the guide grooves 327C and the internalperipheral surface 323A of the cylinder part 323 becomes an acute angle.With the guide grooves 327C, a bending force F1 of the vane 328(equivalent to that F1=“F0 sin θA”) can be reduced. Therefore, even forthe vanes 328 made of carbon whose mechanical strength is lower than ametal complex, the bending force F1 acting on the vanes 328 can beeasily controlled within a tolerable range.

The pump cover 324 is arranged to the front side plate 326 via thegasket 326A, and is fixed to the casing body 322 with a bolt 34. On thefront of the casing body 322, as shown in FIG. 17, a sealing groove 322Dis formed by surrounding the cylinder part 323 and the expansion chamber333, and an annular sealing member 335 is arranged to the sealing groove322D. The exhausting port 324A is provided in the pump cover 324 at aposition corresponding to the expansion chamber 333. The exhausting port324A is intended to exhaust the air which flows into the expansionchamber 333 to the outside of the device (the outside of the vacuum pump301), and a check valve 329 for preventing the countercurrent of airfrom the outside of the device into the pump is attached to theexhausting port 324A.

Next, operations of the vacuum pump 301 are described.

When the rotor 327 is rotationally driven with the operation of theelectric motor 310, the vanes 328 fly outwards along the guide grooves327C by a centrifugal force with the rotation of the rotor 327 so thatthe front ends of the vanes 28 abut with the internal peripheral surface323A of the cylinder part 323. Therefore, As shown in FIG. 17, thecrescent space of the cylinder chamber S is partitioned into 5compression chambers P surrounded by two pieces of mutually adjacentvanes 328 and 328, the outer peripheral surface 327B of the rotor 327and the internal peripheral surface 323A of the cylinder part 323.

In this case, because the center of the cylinder chamber S (=centralaxis X2) is offset from the rotation center X1 of the rotor 327, withthe rotation of the arrow R direction of the rotor 327 with the rotationof the output shaft 312, the flying distances of the vanes 328 fluctuateand the capacity of the compression chamber P is changed to the maximumat a position near the opening 323B and to the minimum at a positionnear the discharging port 323C. Therefore, with the rotation of therotor 327 and the vanes 328, the air taken in one compression chamber Pfrom the opening 323B can rotate and can be compressed with the rotationof the rotor 327, discharged from the discharging port 323C, anddischarged from the exhausting port 324A through the compression chamber333. Thereby, the air which is gas from the vacuum tank connected to thevacuum pump 301 is exhausted and a pressure under an atmosphericpressure (vacuum) can be obtained.

When an underpressure occurs due to the flying out of the vanes 328 inthe guide grooves 327C, there is a fear that this underpressureobstructs the flying out of the vanes 328. In particular, in thisembodiment, because the vanes 328 are made of lightweight carbon and theguide grooves 327C are offset outwards in the radial direction from therotation center X1 of the rotor 327, the centrifugal force acting on thevanes 328 is relatively small and the influence of the aboveunderpressure is easy to be great.

Thus, in this configuration, as shown in FIGS. 18A and 18B, a groove 371that links the plurality of guide grooves 327C is provided on the sidesurface of the rotor 327. Next, the groove 371 is described.

The groove 371 is a groove that links the deepest parts 327D of all theguide grooves 327C, and the groove 371 is formed to a “circular holetype groove” which is a ring-like groove around the rotation center X1.

More specifically, the groove 371 continues endlessly in the peripheraldirection with a constant width narrower than the width of the guidegrooves 327C, and extends so that the deepest parts 327D of all theguide grooves 327C are linked at the inner peripheral side. In thisconfiguration, the internal peripheral edge 101A of the groove 371 islocated at the internal peripheral ends of the deepest parts 327D of theguide grooves 327C, and the outer peripheral edge 101B of the groove 371is located at positions substantially in the middle of the internalperipheral ends and the outer peripheral ends of the deepest parts 327Dof the guide grooves 327C. Thus, there is little processing load addedto the rotor 327, and the groove 371 is formed to a groove shape thathas little influence on the mechanical strength of the rotor 327.

The groove 371 is formed on both side surfaces of the rotor 327.Thereby, spaces that communicate with all the guide grooves 327C can beeasily provided between the two side surfaces of the rotor 327 and theside plates 325 and 326.

Thus, by forming the grooves 371 linking the guide grooves 327C, when anunderpressure is almost produced with the flying out of any vanes 328 inthe guide grooves 327C, the air in other guide grooves 327C can flowpromptly through the above grooves 371 and the occurrence of theunderpressure in the guide grooves 327C can be inhibited.

Besides, because the above grooves 371 link the deepest parts 327D ofthe guide grooves 327C to each other, even if the vanes 328 are at somepositions in the guide grooves 327C, the area where an underpressure isproduced with the flying out of the vanes 328 always communicates withother guide grooves 327C through the grooves 371. Therefore, regardlessof the positions of the vanes 328, the occurrence of the underpressuredue to the flying out of the vanes 328 can be inhibited.

Furthermore, because the vanes 328 that fly out from the guide grooves327 in a centrifugal direction and the vanes 328 that move to theopposite side to the centrifugal direction and return into the guidegrooves 327C exist at the same time in the vane-type rotor 327, byproviding the grooves 371 that link all the guide grooves 327C, air cancome and go through the above grooves 371 between the guide grooves 327Cof the vanes 328 that fly out in the centrifugal direction and the guidegrooves 327C of the vanes 328 that move to the opposite side. Thereby,the so-called pumping loss of all the vanes 328 can be avoided, and thevanes 328 can be easily moved in both directions.

Furthermore, because the grooves 371 are formed on the side surfaces ofthe rotor 327, the grooves 371 can be easily provided without increasingthe number of components and without providing an extra space. Besides,because the grooves 371 are ring-like grooves around the rotation centerX1 of the rotor 327, the grooves can be easily manufactured withoutadversely affecting the rotary balance of the rotor 327. The depth ofthe grooves 371 may be such a depth that the capacity that makes air tobe flowed well between the guide grooves 327C can be ensured, and byadjusting this depth appropriately, it is possible to adjust to acapacity that is most suitable. As described above, according to thepresent embodiment, because the grooves 371 which link the guide grooves327C are provided on the rotor 327, the vanes 328 can easily fly outwithout increasing the number of components. Because the grooves 371 areprovided on the side surfaces of the rotor 327, the grooves 371 can beeasily provided on the rotor 327 with groove-processing.

Furthermore, because the grooves 371 are ring-like grooves that link thedeepest parts 327D of all the guide grooves 327C, the occurrence of anunderpressure due to the flying out of the vanes 328 can be inhibitedregardless of the positions of the vanes 328 and without affecting therotation balance of the rotor 327. The groove 371 may be provided onlyon one side surface of the rotor 327 when the vanes 328 can easily flyout sufficiently with the groove 371 only on the one side surface of therotor 327.

FIGS. 19A and 19B show a second embodiment to achieve the fourth object,in which FIG. 19A is a figure which shows a side surface of the rotor327 with the neighboring configuration, and FIG. 19B shows a B-B sectionof FIG. 19A.

In the second embodiment, a “counterbored hole type groove” is shown,that is, the groove 371 to be formed on a side surface of the rotor 327is formed to a groove of a counterbored hole shape (included in annulargrooves) around the rotation center X1.

The outer peripheral edge 101B, which is centered on the rotation centerX1, of the groove 371 is located at positions substantially in themiddle of the internal peripheral ends and the outer peripheral ends ofthe deepest parts 327D of the guide grooves 327C. The groove 371 isformed to a groove of a perfect circle shape whose inside is all sunk,and links the deepest parts 327D of all the guide grooves 327C.

Therefore, by providing the groove 371, the same effects as those of theabove first embodiment, such as that the vanes 328 can easily fly out,can be achieved without increasing the number of components.

Besides, in the case of the groove 371, the axial bore 327A of the rotor327 can communicate with all the guide grooves 327C.

Although the front end part 312A of the output shaft 312 is insertedthrough the axial bore 327A of the rotor 327, some gaps are formedbetween the axial bore 327A and the output shaft 312 even in the case ofspline combination or key combination, and when the vacuum pump 301 isoperated, the air pressure (pressure) of the center side of the rotor327 is high, and the pressure of the gaps becomes the atmosphericpressure in the vacuum pump 301.

Therefore, with the configuration that the guide grooves 327C and theaxial bore 327A of the rotor 327 communicate, the high pressure airwhich is the high pressure fluid in the axial bore 327A or near theaxial bore 327A can be introduced into the guide grooves 327C, and byusing this high pressure air, the vanes 328 can easily fly out.

As described above, according to the present embodiment, because thegroove 371 which links the guide grooves 327C and the axial bore 327A ofthe rotor 327 is provided on the rotor 327, by using the centrifugalforce and the high pressure fluid at the side of the axial bore 327A,the vanes 328 can more easily fly out. The groove 371 may be provided onboth side surfaces of the rotor 327 or may be provided on one sidesurface of the rotor 327.

FIGS. 19A and 19B show a third embodiment to achieve the fourth object,in which FIG. 19A is a figure which shows a side surface of the rotor327 with the neighboring configuration, and FIG. 19B shows a B-B sectionof FIG. 19A.

In the third embodiment, a “groove with a labyrinth” is shown, that is,in addition to a groove 371 that links the guide grooves 327C, alabyrinth passage 381 between the guide grooves 327C and the axial bore327A are included on a side surface of the rotor 327.

The labyrinth passage 381 is formed by coaxially arranging a pluralityof (in the present embodiment three) annular grooves 381A withintervals, and the plurality of annular grooves 381A are providedcoaxially with the axial bore 327A.

The cylinder chamber S of the vacuum pump 301 is sealed basically exceptthe opening 323B and the discharging ports 323C and 322C, but because anopening where wires that extend from electrical components such as theelectric motor of the vacuum pump 301 are drawn outwards is necessary,air might go in and out through gaps such as the opening. For example,in the cylinder chamber S, because the air pressure (pressure) of thecentral side of the rotor 327 becomes higher when the vacuum pump 301 isoperated, a flow of the air of the central side discharged through thethrough hole 361D which is the bore near the bearing (shaft bearing) 362may be produced.

When this flow is produced, abrasion powder which is produced because ofthe sliding of the vanes 328 may be attached to the bearing 362, and itis desired that the attachment of the abrasion powder is avoided.

As described above, in this configuration, because the labyrinth passage381 is provided between the guide grooves 327C and the axial bore 327A,it is hard for the abrasion powder which is produced at the side of thevanes 328 to flow to the center side of the rotor 327. Therefore, it canbe prevented that the abrasion powder flows to the central side of therotor 327 and flows to the bearing 362.

Further, because the labyrinth passage 381 is formed as a multi-ringsshaped groove formed on the side surface of the rotor 327, the labyrinthpassage 381 can be provided without increasing the number of components,without providing another space separately and without adverselyaffecting the rotation balance of the rotor 327. Besides, the grooveprocessing of the labyrinth passage 381 and the groove processing of thegroove 371 which links the guide grooves 327C can be performed at thesame time.

The labyrinth passage 381 may be provide on the two side surfaces of therotor 327 and may be provided on one side surface, but it is desirablethat the labyrinth passage 381 is provided at least on the side surfaceof the rotor 327 at the side of the bearing 362.

FIG. 20 is a figure which enlarges and shows the output shaft 312 of theelectric motor 310 with the neighboring configuration.

As shown in this figure, the output shaft 312 of the electric motor 310is provided with a disc-like collar part 385 whose diameter is largerthan that of the output shaft 312. The collar part 385 is a member thatfunctions as a shielding collar part for shielding the abrasion powderwhich is produced at the side of the vanes 328 from flowing to thebearing 362, and is arranged between the bearing 362 and the side plate325.

According to this configuration, the abrasion powder produced at theside of the vanes 328 can be more surely shielded by the collar part 385which the output shaft 312 is provided with from flowing to the bearing362.

The collar part 385 may be formed integrally with the output shaft 312,and it is also possible that the collar part 385 is formed of acomponent other than the output shaft 312 and is attached to the outputshaft 312. The shape of collar part 385, such as the outer diameter, maybe changed optionally as far as the abrasion powder can be shielded fromflowing to the side of the bearing 362.

The labyrinth passage 381 of this embodiment has a shape formed bycoaxially arranging a plurality of (in the present embodiment three)annular grooves 381A with intervals, but the shape of the labyrinthpassage 381 is not limited to this, and may have eddy-like annulargrooves (eddy grooves).

FIGS. 21A and 21B show a fourth embodiment to achieve the fourth object,in which FIG. 21A is a figure which shows a side surface of the rotor327 with the neighboring configuration, and FIG. 21B shows a B-B sectionof FIG. 21A.

In the fourth embodiment, a “star type groove” is shown, that is,grooves 375 that link the guide grooves 327C and the axial bore 327A ofthe rotor 327 are provided on a side surface of the rotor 327. Thegrooves 375 is formed of a plurality of (in the present embodiment five)grooves that link all (in the present embodiment five) the guide grooves327C and the axial bore 327A, respectively.

In this configuration, the guide grooves 327C are offset to positionsapart from the axial bore 327A, and the above mentioned grooves 375 areformed to grooves that extend into a linear shape along the radialdirection of the rotary shaft (the rotation center X1) of the rotor 327,and are connected to the deepest parts 327D of the guide grooves 327C.

Thus, if the grooves 375 which link the guide grooves 327C and the axialbore 327A of the rotor 327 are provided, when the vacuum pump 301 isoperated, the high pressure air which is the high pressure fluid of thecenter side of the rotor 327 can be introduced into the guide grooves327C, and the vanes 328 can easily fly out.

Besides, because the grooves 375 extends into a linear shape along theradial direction of the rotary shaft (the rotation center X1) of therotor 327, while the guide grooves 327C and the axial bore 327A of therotor 327 can be linked at the shortest distance, the high pressure aircan be sent to the side of the guide grooves 327C by using thecentrifugal force of the rotor 327 and the high pressure air can besmoothly introduced into the guide grooves 327C. Therefore, the vanes328 can more easily fly out efficiently.

Further, because the grooves 375 can be easily provided with processingson the side surface of the rotor 327, the grooves 375 can be providedwithout increasing the number of components, without providing anotherspace separately and without adversely affecting the rotation balance ofthe rotor 327.

Further, the grooves 375 can function as grooves that connect all theguide grooves 327C through the axial bore 327A of the rotor 327.Therefore, through the grooves 375, air can come and go between theguide grooves 327C where the vanes 328 fly out in the centrifugaldirection and the guide grooves 327C where the vanes 328 move to theopposite side, and thereby the vanes 328 can be easily moved.

In this embodiment, it is described that the grooves 375 which link theguide grooves 327C and the axial bore 327A of the rotor 327 are thegrooves that link the guide grooves 327C and the axial bore 327A of therotor 327 at the shortest distance, but the invention is not limited tothis, the grooves 375 may have a curve groove shape that is curvedconvexly towards the outer peripheral side of the rotor 327. If thegrooves 375 have a curve groove shape, the inclination of the grooves375 changes in accordance with the radial direction of the rotor 327,and the grooves longer than the shortest distance between the guidegrooves 327C and the axial bore 327A of the rotor 327 can be providedand can function as a labyrinth passage so that it is hard for theabrasion powder which occurs at the side of the vanes 328 to flow to thecenter side of the rotor 327.

The preferred embodiments for performing the present invention aredescribed as above, but the present invention is not limited to thepreviously described embodiments, and various modifications and changesare possible based on the technical thought of the present invention.

For example, in the above embodiments, it is also possible to form abypath 391 of the fluid (air) between the vanes 328 and the guidegrooves 327C by cutting one edge of the vanes 328. FIG. 22 is a figurewhich shows a configuration example in this case.

In FIG. 23, by cutting the side surfaces of the vanes 328, the width328W of the vanes 328 becomes smaller than the width 327W of the rotor327. In this configuration, between the vanes 328 and side plates 325and 326 (in this example side plate 325), a gap that becomes the bypath391 is formed. Therefore, when an underpressure is almost produced inthe guide grooves 327C with the flying out of the vanes 328, as shownwith an arrow in FIG. 23, air can flow into the guide grooves 327Cthrough the above bypath 391. Thereby, the occurrence of theunderpressure in the guide grooves 327C can be inhibited, and the vanes328 can easily fly out. Besides, the bypath of the fluid between thevanes 328 and the guide grooves 327C may be formed by cutting partsother than the side surfaces of the vanes 328.

In the above embodiments, it is described that the ring-like grooves 371which link all the guide grooves 327C are provided, but the invention isnot limited to this, the groove shape may be changed appropriately asfar as the vanes can be easily fly out. In the above embodiments, it isdescribed that the present invention is applied into the vane-typevacuum pump, but the invention is not limited to this, and the presentinvention may be applied into other vane-type compressing devicesbesides the vacuum pump.

FIG. 24 is a side partial sectional view of a vacuum pump 401 accordingto the embodiment of the invention to achieve the fifth object. FIG. 25is a figure of the vacuum pump 401 of FIG. 24 when viewed from the frontside of the vacuum pump 401 (the right side in the figure above).However, FIG. 25 illustrates a state that those members such as a pumpcover 424 and a side plate 426 are removed in order to show theconfiguration of a cylinder chamber S. In the following, for theconvenience of description, the directions respectively indicated by thearrows in the upper parts of FIGS. 24 and 25 are the up, down, front,rear, right and left directions of the vacuum pump 401. The front-reardirection is an axial direction, and the right-left direction is awidthwise direction.

The vacuum pump 401 shown in FIG. 24 is a rotary vane-type vacuum pump,and, for example, is used as a vacuum source of a brake boosting device(not shown in the figure) of an automobile or the like. In this case,the vacuum pump 401 is usually arranged in an engine room and isconnected with pipes to the brake boosting device through a vacuum tank(not shown in the figure). The use range of the vacuum pump 401 used forautomobiles or the like is, for example, −60 kPa to −80 kPa.

As shown in FIG. 24, the vacuum pump 401 includes an electric motor 410and a pump body 420 which is operated by using the electric motor 410 asa driving source, and the electric motor 410 and the pump body 420 arefixed to and supported by a vehicle body of, for example, an automobilein an integrally connected state.

The electric motor 410 has an output shaft (rotary shaft) 412 whichextends substantially from the center of one end (front end) of a case411, which is formed into a substantially cylindrical shape, towards theside of the pump body 420 (front side). The output shaft 412 rotatesaround a rotation center X1 that extends in the front-rear direction. Aspline part 412B, which is fitted into a rotor 427 of the pump body 420to be described below and turns and stops the rotor 427, is formed atthe front end part 12A of the output shaft 412. By providing a key onthe outside surface of the output shaft 412, skidding of the rotor 427can be prevented.

When a power supply (not shown in the figure) is switched ON, the outputshaft 412 of the electric motor 410 rotates in an arrow R direction(counterclockwise direction) in FIG. 25, and thereby the rotor 427 isrotated in the same direction (arrow R direction) around the rotationcenter X1.

The case 411 includes a case body 460, which is formed to a bottomedcylindrical shape, and a cover body 461 which blocks the opening of thecase body 460, and the case body 460 is formed by bending a peripheralpart 460A of the case body 60 outwards. The cover body 461 is integrallyformed by including a disk part (wall surface) 461A which is formed tohave substantially the same diameter as that of the opening of the casebody 460, a cylinder part 461B which is connected to the fringe of thedisk part 461A and is fitted into the internal peripheral surface of thecase body 460, and a flexed part 461C which is formed by bendingoutwards the fringe of the cylinder part 461B, the disk part 461A andthe cylinder part 461B enter into the case body 460, and the flexed part461C abuts against and is fixed to the peripheral part 460A of the casebody 460. Thereby, in the electric motor 410, one end (front end) of thecase 411 is caved inwards, and a fitting cavity 463, which the pump body420 is attached to in a pillbox fitting manner, is formed.

Approximately in the center of the disk part 461A, a through hole 461Dwhere the output shaft 412 penetrates and a circular bearing holdingpart 461E which extends inside of the case body 460 around the throughhole 461D are formed, and the outer ring of a bearing 462 that pivotallysupports the above output shaft 412 is held by the internal peripheralsurface 61F of the bearing holding part 461E. In the embodiment, anopen-type ball bearing is adopted for the bearing 462. Because theopen-type ball bearing has a smaller resistance at the time of rotationand lower mechanical loss than a shield-type ball bearing, the powerconsumption of the electric motor can be reduced.

The pump body 420 includes, as shown in FIG. 24, a casing body 422 whichis fitted into the fitting cavity 463 which is formed at the front sideof the case 411 of the electric motor 410, a cylinder part 423 which ispress fitted in the casing body 422 and forms a cylinder chamber S, anda pump cover 424 which covers the casing body 422 from the front side.In this embodiment, a casing 431 of the vacuum pump 401 is formed byincluding the casing body 422, the cylinder part 423 and the pump cover424.

The casing body 422 uses, for example, metal materials such as aluminumwhose thermal conductivity is high, and as shown in FIG. 25, the shapeof the casing body 422, when viewed from front, is formed to asubstantially rectangular shape which is longer in the up-down directionwith the above-mentioned rotation center X1 as an approximate center. Acommunicating hole 422A, which communicates with the cylinder chamber Swhich the casing body 422 is provided with, is formed in the upper partof the casing body 422, and a vacuum absorbing nipple 430 is pressfitted to the communicating hole 422A. As shown in FIG. 24, the vacuumabsorbing nipple 430 is a direct pipe which extends upwards, and a pipeor a tube which supplies underpressure air from an external equipment(for example, a vacuum tank (not shown in the figure)) is connected toone end 430A of the vacuum absorbing nipple 430.

A bore 422B around a central axis X2 which extends in the front-reardirection is formed in the casing body 422, and a cylinder part 423which is formed to a cylindrical shape is press fitted into the bore422B. The central axis X2 is parallel with the rotation center X1 of theoutput shaft 412 of the above-mentioned electric motor 410, and as shownin FIG. 25, is offset to the upper left side relative to the rotationcenter X1. In this configuration, the central axis X2 is offset so thatthe outer peripheral surface 427B of the rotor 427 around the rotationcenter X1 is adjacent to the internal peripheral surface 423A of thecylinder part 423 that is formed around the central axis X2.

The cylinder part 423 is formed of metal material (in the presentembodiment, iron) which is the same as that of the rotor 427. With thisconfiguration, because the thermal expansion coefficients of thecylinder part 423 and the rotor 427 are the same, regardless oftemperature change of the cylinder part 423 and the rotor 427, thecontact of the outer peripheral surface 427B of the rotor 427 and theinternal peripheral surface 423A of the cylinder part 423 when the rotor427 is rotated can be prevented. The cylinder part 423 and the rotor 427may use different materials as long as they are metal materials thathave substantially the same thermal expansion coefficient.

Because the cylinder part 423 can be accommodated in the length range ofthe front-rear direction of the casing body 422 by press fitting thecylinder part 423 into the bore 422B which is formed in the casing body422, the cylinder part 423 is prevented from being protruded from thecasing body 422 and the casing body 422 can be downsized.

Furthermore, the casing body 422 is formed of material whose thermalconductivity is higher than that of the rotor 427. Thereby, since theheat that is generated when the rotor 427 and vanes 428 are rotationallydriven can be transmitted to the casing body 422 immediately, the heatfrom the casing body 422 can be dissipated sufficiently.

An opening 423B which is coupled with the communicating hole 422A of theabove described casing body 422 and the cylinder chamber S is formed atthe cylinder part 423, and the air passing through the vacuum absorbingnipple 430 is supplied to the cylinder chamber S through thecommunicating hole 422A and the opening 423B. Therefore, in thisembodiment, an intake path 32 is formed by including the vacuumabsorbing nipple 430, the communicating hole 422A of the casing body 422and the opening 423B of the cylinder part 423. At the lower part of thecasing body 422 and the cylinder part 423, discharging ports 422C and423C, which penetrate the casing body 422 and the cylinder part 423 andwhere the air compressed in the cylinder chamber S is exhausted, areprovided.

Side plates 425 and 426 are disposed at the rear end and the front endof the cylinder part 423, respectively. The diameter of the side plates425 and 426 is set to be larger than the inside diameter of the internalperipheral surface 423A of the cylinder part 423. The side plates 425and 426 are pressed against the front end and the rear end of thecylinder part 423, respectively, by being biased by gaskets 425A and26A. Thereby, the sealed cylinder chamber S is formed inside thecylinder part 423 except the opening 423B which is coupled to the vacuumabsorbing nipple 430 and the discharging ports 423C and 422C.

In the cylinder chamber S, the rotor 427 is disposed. The rotor 427 isformed into a thick cylindrical shape, and the output shaft 412 on whichthe above-mentioned spline part 4128 is formed is fitted to the internalperipheral surface 27A of the rotor 427. With this spline fittingconfiguration, the rotor 427 is rotated integrally with the output shaft412. The length in the front-rear direction of the rotor 427 is set tobe substantially equal to the length of the cylinder part 423, namely,the distance between the mutually opposed inside surfaces of theabove-mentioned two pieces of side plates 425 and 426. The outerdiameter of the rotor 427 is set so that, as shown in FIG. 25, the outerperipheral surface 427B of the rotor 427 keeps a minute clearance from apart among the internal peripheral surface 423A of the cylinder part 423that is located at the lower right side. Thereby, as shown in FIG. 25, aspace of a crescent shape is formed between the outer peripheral surface427B of the rotor 427 and the internal peripheral surface 423A of thecylinder part 423.

The rotor 427 is provided with a plurality of (in this example, fivepieces) vanes 428 which partition the crescent space. The vane 428 isformed into a board shape, and the length in the front-rear direction isset to be substantially equal to the distance between the mutuallyopposed inside surfaces of the two pieces of side plates 425 and 426,like the rotor 427. These vanes 428 are disposed to be extendable fromthe guide grooves 427C which the rotor 427 is provided with. The vanes428 are protruded outwards along the guide grooves 427C by a centrifugalforce with the rotation of the rotor 427 so that the front ends of thevanes 428 abut with the internal peripheral surface 423A of the cylinderpart 423. Thereby, the above-mentioned crescent space is partitionedinto 5 compression chambers P surrounded by two pieces of mutuallyadjacent vanes 428 and 428, the outer peripheral surface 427B of therotor 427 and the internal peripheral surface 423A of the cylinder part423. These compression chambers P rotates in the same direction with therotation of the arrow R direction of the rotor 427 with the rotation ofthe output shaft 412, and the capacity of each of these compressionchambers P becomes bigger at positions near the opening 423B, andbecomes smaller at positions near the discharging port 423C. That is,with the rotation of the rotor 427 and the vanes 428, the air taken inone compression chamber P from the opening 423B rotates and iscompressed with the rotation of the rotor 427, and is discharged fromthe exhausting port 423C. In this configuration, the rotary compressingelements are formed by including the rotor 427 and the plurality ofvanes 428.

In this configuration, the cylinder part 423 is formed in the casingbody 422, as shown in FIG. 25, by offsetting the central axis X2 of thecylinder part 423 to the upper left side relative to the rotation centerX1. Therefore, in the casing body 422, a big space in the directionopposite to that the cylinder part 423 is offset can be secured, and theexpansion chamber 433 which communicates with the discharging ports 423Cand 422C is formed in this space along the peripheral part of thecylinder part 423.

The expansion chamber 433 is formed as a big closed space along theperipheral part of the cylinder part 423 from a position below thecylinder part 423 to a position above the output shaft 412, andcommunicates with the exhausting port 424A which is formed in the pumpcover 424. After the compressed air which flows into the expansionchamber 433 is expanded and scattered in the expansion chamber 433, theair hits the wall of the expansion chamber 433 and is reflecteddiffusely. Thereby, since the sound energy of the compressed air isattenuated, the noise and the vibration in the air-exhausting can bereduced. In the embodiment, an exhausting path 437 is formed byincluding the discharging ports 422C and 423C, which are formed in thecasing body 422 and the cylinder part 423, respectively, the expansionchamber 433 and the exhausting port 424A.

In this embodiment, by arranging the cylinder part 423 to be offset fromthe rotation center X1 of the rotor 427, a big space at the peripheralpart of the cylinder part 423 at the side of the above mentionedrotation center X1 can be ensured in the casing body 422. Therefore,because the expansion chamber 433 can be integrally formed in the casingbody 422 by forming the big expansion chamber 433 in this space, it isnot necessary to provide the expansion chamber 433 outside the casingbody 422, the casing body 422 can be downsized and thus the vacuum pump401 can be downsized.

The pump cover 424 is arranged to the front side plate 426 via a sealingring 426A, and is fixed to the casing body 422 with a bolt 66. On thefront of the casing body 422, as shown in FIG. 25, a sealing groove 422Dis formed by surrounding the cylinder part 423 and the expansion chamber433, and an annular sealing member 467 is arranged to the sealing groove422D. The exhausting port 424A is provided in the pump cover 424 at aposition corresponding to the expansion chamber 433. The exhausting port424A is intended to exhaust the air which flows into the expansionchamber 433 to the outside of the device (the outside of the vacuum pump401), and a check valve 429 for preventing the countercurrent of airfrom the outside of the device into the pump is attached to theexhausting port 424A.

FIG. 26 is a rear view of the casing body 422.

As mentioned above, the vacuum pump 401 is formed by coupling theelectric motor 410 and the pump body 420, and the rotor 427 connected tothe output shaft 412 of the electric motor 410 and the vanes 428 slidein the cylinder part 423 of the pump body 420. Therefore, it isimportant to assemble the pump body 420 in accordance with the rotationcenter X1 of the output shaft 412 of the electric motor 410.

Therefore, in this embodiment, as mentioned above, the fitting cavity463, which is centered on the rotation center X1 of the output shaft412, is formed at one end of the case 411 of the electric motor 410. Onthe other hand, on the back of the casing body 422, as shown in FIG. 26,a cylindrical fitting part 422F is integrally formed to be protrudedbackwards around the cylinder chamber S. The fitting part 422F is formedconcentrically with the rotation center X1 of the output shaft 412 ofthe electric motor 410, and is formed so that the outer edge of thefitting part 422F is engaged with the fitting cavity 463 of the electricmotor 410 in a pillbox manner. Furthermore, a chamfering process isperformed at the corners 422G of the fitting part 422F so that thecasing body 422 can be easily fitted in the fitting cavity 463 of theelectric motor 410.

Therefore, with this configuration, since only by fitting the fittingpart 422F of the casing body 422 into the fitting cavity 463 of theelectric motor 410, the central locations can be easily put together,the assembly of the electric motor 410 and the pump body 420 can beeasily performed. Further, on the back of the casing body 422, a sealinggroove 422E is formed around the fitting part 422F, and a circularsealing member 435 is arranged to the sealing groove 422E.

In the vacuum pump 401 of the present embodiment, the fitting part 422Fof the casing body 422 is fitted in and fixed to the fitting cavity 463the electric motor 410. Because the cylinder body 423 forming thecylinder chamber S is arranged in the inside of the fitting part 422F asshown in FIG. 24, and the side plate 425 is arranged at the side of therear end (the electric motor 410) of the cylinder body 423, a minutespace 470 is formed between the side plate 425 and the disk part 461A ofthe electric motor 410.

On the other hand, because the side plates 425 and 426 and the rotor 427do not always adhere when the vacuum pump 401 is operated, air is drawnfrom the above described space 470 through gaps between the side plates425 and 426 and the rotor 427 and a gap between the axial bore 27A ofthe rotor 427 and the output shaft 412 since an underpressure occurs inthe compression chambers P, and the pressure of the space 470 may becomelower than the atmospheric pressure (that is, underpressure).

Then, a flow of the air in the case 411 of the electric motor 410 thatflows into the above mentioned space 470 through the through hole 461Dwhich is a bore near the open-type bearing (shaft bearing) 462 mayoccur. When this flow occurs, abrasion powder which occurs because ofthe sliding of, for example, the brush of the electric motor 410 may beattached to the bearing 462, and it is desired that the attachment ofthe abrasion powder is avoided.

In this configuration, in order to prevent an underpressure in theminute space 470 formed between the side plate 425 and the disk part461A of the electric motor 410, a communicating hole 471 of a small size(in the present embodiment 1.6mm in diameter) that communicates thespace 470 and the expansion chamber (other space) 433 whose pressure isabove the atmospheric pressure is formed in the casing body 422. Thus,when the pressure of the space 470 is below the atmospheric pressure, asshown in FIG. 27, since the air whose pressure is above the atmosphericpressure flows into the space 470 through the communicating hole 471,the pressure of the space 470 is immediately restored to the atmosphericpressure (or above the atmospheric pressure). Therefore, by inhibitingthat the air in the case 411 of the electric motor 410 flows into thespace 470 through the through hole 461D, it can be avoided that theabrasion powder included in the air is attached to the bearing 462, anda durability drop of the bearing 462 can be prevented and thus adurability drop of the electric motor 410 can be prevented.

In this case, because air flows into the pump body 420 through thecommunicating hole 471, a drop of the vacuum degree in the externalequipment may be concerned about. However, it becomes clear with anexperiment that by forming the communicating hole 471, there is not atrouble at all. The biggest underpressure level is only slightlydecreased (−95 kPa, −93 kPa) and is in the normal use range (forexample, −60 kPa to −80 kPa) in a brake boosting device of anautomobile.

The communicating hole 471 is formed, as shown in FIG. 25, above theoutput shaft 412 at a position that is near the cylinder part 423 at theupper part of the expansion chamber 433.

Even if the communicating hole 471 is formed at some position of theexpansion chamber 433, as long as the position communicates with thespace 470, the cancellation of the underpressure of the space 470 can beimplemented. However, when the communicating hole is provided below theexpansion chamber 433, namely, near the exhausting port 424A, there arethe following problems.

In the cylinder chamber S, because the vanes are gradually worn when thevanes slide on the internal peripheral surface 423A of the cylinderchamber S, the air that contains abrasion powder is easy to be exhaustednear the exhausting port 424A. Therefore, a problem occurs that when thecommunicating hole is provided near the exhausting port 424A, since theair that contains abrasion powder flows into the space 470 through thecommunicating hole, the abrasion powder is attached to the bearing 462.When it is assumed that rain water invades into the expansion chamber433 through the exhausting port 424A, if the communicating hole isprovided near the exhausting port 424A, it is possible that the rainwater flows into the above space 470 through the communicating hole. Inthis case, because the electric motor 410 is next to the space 470, itis necessary to surely prevent the water from flowing into the electricmotor 410.

In order to inhibiting the occurrence of these problems, in the presentembodiment, the communicating hole 471 is formed above the output shaft412 at the upper part of the expansion chamber 433. Therefore, even ifabrasion powder or water invades into the expansion chamber 433 by anychance, because the abrasion powder or water is less likely to be movedto be higher than the output shaft 412, it can be prevented that theabrasion powder or water flows into the space 470 through thecommunicating hole 471.

Thus, in this embodiment, the communicating hole 471 communicating theminute space 470 which is formed between the side plate 425 and the diskpart 461A of the electric motor 410 and the expansion chamber (otherspace) 433 whose pressure is above the atmospheric pressure is formed inthe casing body 422. Therefore, by inhibiting that the air in the case411 of the electric motor 410 flows into the above space 470 through thethrough hole 461D, it can be avoided that the abrasion powder includedin the air is attached to the bearing 462. On the other hand, becausethe temperature in the case 411 of the electric motor 410 increasesduring the operation of the vacuum pump 401, it is necessary topositively exhaust the expanded air due to the temperature increase tothe outside of the case 411.

Because the electric motor 410 is formed to a waterproof type, the casebody 460 is not provided with an opening that becomes an exhaustingport. Therefore, if no measure is taken, the expanded air due to thetemperature increase will be exhausted through the through hole 461Dwhich is a bore near the open-type bearing (shaft bearing) 462, and aproblem occurs that the abrasion powder produced due to the sliding of,for example, the brush of the electric motor 410 may be attached to thebearing 462.

Therefore, in this embodiment, in the electric motor 410, an exhaustingport (communicating hole) 472 is formed in the disk part 461A opposed tothe fitting part 422F of the casing body 422, at a position that ishigher than the bearing 462 in the disk part 461A of the case 411,namely, as shown in FIG. 24, a position right above the output shaft412. Because the expanded air due to the temperature increase isexhausted through the exhausting port 472 when the temperature in thecase 411 increases, by inhibiting that the air in the case 411 of theelectric motor 410 is exhausted through the through hole 461D, it can beavoided that the abrasion powder included in the air is attached to thebearing 462, and a durability drop of the bearing 462 can be preventedand thus a durability drop of the electric motor 410 can be prevented.

Furthermore, in this embodiment, since the air exhausted from theexhausting port 472 flows into the above space 470 through a gap withthe sealing ring 425A, the exhausting port 472 will communicate with thespace 470 through the sealing ring 425A. Therefore, the exhausting port472 functions as a communicating hole that communicates the space 470with the inside of the case 411 of the electric motor 410 (a space whosepressure is above the atmospheric pressure) during the operation of thevacuum pump 401.

Because the exhausting port 472 is formed at a position that is higherthan the bearing 462 in the disk part 461A of the case 411, the abrasionpowder in the case 411 can be inhibited from being exhausted through theexhausting port 472, and water can be inhibited from invading into thecase 411 through the exhausting port 472.

As described above, according to the present embodiment, in the vacuumpump 401 which includes the casing 431 attached to the disk part 461A ofthe case 411 of the electric motor 410, the rotor 427 rotationallydriven by the output shaft 412 of the electric motor 410 in the casing431, and a plurality of vanes 428 extendably accommodated in the rotor427, the casing 431 includes the hollow cylinder chamber S which isdriven by the rotor 427 and has the openings at the ends, and the sideplates 425 and 426 which blocks the openings of the cylinder chamber S,and the communicating hole 471, which communicates the space 470, whichis formed between the side plate 425 and the disk part 461A of theelectric motor 410, and the expansion chamber 433, which is formed inthe exhausting path 437 to link the cylinder chamber S and theexhausting port 424A, is included. Therefore, when the pressure of theabove space 470 is below the atmospheric pressure, since the air in theexpansion chamber 433 whose pressure is above the atmospheric pressureflows into the space 470 through the communicating hole 471, thepressure of the space 470 is immediately restored to the atmosphericpressure (or above the atmospheric pressure). Therefore, by inhibitingthat the air in the case 411 of the electric motor 410 flows into theabove space 470, a durability drop of the bearing 462 of the electricmotor 410 due to the abrasion powder included in the air can beprevented, and thus a durability drop of the electric motor 410 can beprevented.

According to the present embodiment, the casing body 422 forming thecasing 431 includes the expansion chamber 433, which is formed in theexhausting path 437 to link the cylinder chamber S and the exhaustingport 424A, at the peripheral part of the cylinder chamber S. Therefore,the cylinder chamber S and the expansion chamber 433 can be integrallyformed in the casing body 422, and the upsizing of the vacuum pump 401can be inhibited. Furthermore, because the communicating hole 471 thatcommunicates the expansion chamber 433 and the space 470 is formed inthe casing body 422, the air in the expansion chamber 433 can easilyflow into the above space 470. According to the present embodiment, thecommunicating hole 471 is formed at a position that is higher than theoutput shaft 412 in the expansion chamber 433. Therefore, even ifabrasion powder or water invades into the expansion chamber 433 by anychance, because the abrasion powder or water is less likely to be movedto be higher than the output shaft 412, it can be prevented that theabrasion powder or water flows into the space 470 through thecommunicating hole 471.

According to the present embodiment, the electric motor 410 includes thebearing 462 that pivotally supports the output shaft 412, and theexhausting port 472 is formed in the disk part 461A of the case 411 at aposition that is higher than the bearing 462. Therefore, since theexpanded air due to the temperature increase is exhausted through theexhausting port 472 when the temperature in the case 411 increases, byinhibiting that the air in the case 411 of the electric motor 410 isexhausted through the through hole 461D, it can be avoided that theabrasion powder included in the air is attached to the bearing 462, anda durability drop of the bearing 462 can be prevented and thus adurability drop of the electric motor 410 can be prevented.

The preferred embodiments for performing the present invention aredescribed as above, but the present invention is not limited to thepreviously described embodiments, and various modifications and changesare possible based on the technical thought of the present invention.For example, in this embodiment, the exhausting port 472 is provided inthe disk part 461A opposed to the fitting part 422F of the casing body422 and right above the output shaft 412, but the invention is notlimited to this and the exhausting port may be provided at the innerside of the sealing ring 425A and above the bearing 462. In this case, awater draining hole may be provided in the disk part 461A of the case411 of the electric motor 410 at a position that is lower than thebearing 462. The water draining hole is a hole where water is exhaustedoutside when the water invades into the case 411 by any chance, and itis desirable that the water draining hole is provided in the disk part461A at a position as low as possible. The water draining hole, like theabove described exhausting port 472, functions as a communicating holethat communicates the space 470 with the inside of the case 411 of theelectric motor 410 (a space whose pressure is above the atmosphericpressure) during the operation of the vacuum pump 401.

FIG. 28 is a schematic diagram of a brake device 500 in which a vacuumpump 501 according to the embodiment of the invention to achieve thefirst object is used as a vacuum source. For example, the brake device500 includes front brakes 502 a and 502 b which are attached to theright and left front wheels of a vehicle such as an automobile, and rearbrakes 503 a and 503 b which are attached to the right and left rearwheels. These brakes are connected with a master cylinder 504 via braketubes 509, respectively, and each brake is operated with an oil pressurewhich is sent through the brake tube 509 from the master cylinder 504.

The brake device 500 further includes a brake booster 506 (brakeboosting device) which is connected with a brake pedal 505, and a vacuumtank 507 and the vacuum pump 501 is serially connected to the brakebooster 506 through an air tube 8. The brake booster 506 is adapted toboost the pedal force of the brake pedal 505 using an underpressure inthe vacuum tank 507, and when a piston (not shown in the figure) of themaster cylinder 504 is moved by a small pedal force, an enough brakingpower will be got.

The vacuum pump 501 is arranged in an engine room of the vehicle, andexhausts air in the vacuum tank 507 to the outside of the vehicle sothat there becomes a vacuum in the vacuum tank 507. The use range of thevacuum pump 501 used for automobiles or the like is, for example, −60kPa to −80 kPa.

FIG. 29 is a side partial sectional view of the vacuum pump 501, andFIG. 30 is a figure of the vacuum pump 501 of FIG. 29 when viewed fromthe front side of the vacuum pump 501 (the right side in the figure).However, FIG. 30 illustrates a state that those members such as a pumpcover 524 and a side plate 526 are removed in order to show theconfiguration of a cylinder chamber S. In the following, for theconvenience of description, the directions respectively indicated by thearrows in the upper parts of FIGS. 29 and 30 are the up, down, front,rear, right and left directions of the vacuum pump 501. The front-reardirection is an axial direction, and the right-left direction is awidthwise direction.

As shown in FIG. 29, the vacuum pump 501 includes an electric motor(driving machine) 510 and a pump body 520 which is operated by using theelectric motor 510 as a driving source, and the electric motor 510 andthe pump body 520 are fixed to and supported by a vehicle body of, forexample, an automobile in an integrally connected state.

The electric motor 510 has an output shaft (rotary shaft) 512 whichextends substantially from the center of one end (front end) of a case511, which is formed into a substantially cylindrical shape, towards theside of the pump body 520 (front side). The output shaft 512 functionsas a driving shaft for driving the pump body 520, and the output shaft12 rotates around a rotation center X1 extending in the front-reardirection. A front end part 512A of the output shaft 512 is formed to aspline shaft and is engaged with a shaft hole 527A where the rotor 527of the pump body 520 is penetrated in the axial direction, so that theoutput shaft 512 and the rotor 527 are connected to be integrallyrotatable. Instead of that the output shaft 512 and the rotor 527 arespline coupled, the output shaft 312 and the rotor 327 may be coupledthrough a key.

When a power supply (not shown in the figure) is switched ON, the outputshaft 512 of the electric motor 510 rotates in an arrow R direction(counterclockwise direction) in FIG. 30, and thereby the rotor 527 isrotated in the same direction (arrow R direction) around the rotationcenter X1.

The case 511 includes a case body 560, which is formed to a bottomedcylindrical shape, and a cover body 561 which blocks the opening of thecase body 560, and the case body 560 is formed by bending a peripheralpart 560A of the case body 60 outwards. The cover body 561 is integrallyformed by including a disk part (wall surface) 561A which is formed tohave substantially the same diameter as that of the opening of the casebody 560, a cylinder part 561B which is connected to the fringe of thedisk part 561A and is fitted into the internal peripheral surface of thecase body 560, and a flexed part 561C which is formed by bendingoutwards the fringe of the cylinder part 561B, the disk part 561A andthe cylinder part 561B enter into the case body 560, and the flexed part561C abuts against and is fixed to the peripheral part 560A of the casebody 560. Thereby, in the electric motor 510, one end (front end) of thecase 511 is caved inwards, and a fitting cavity 563, which the pump body520 is attached to in a pillbox fitting manner, is formed.

Approximately in the center of the disk part 561A, a through hole 561Dwhere the output shaft 512 penetrates and a circular bearing holdingpart 561E which extends inside of the case body 560 around the throughhole 561D are formed, and the outer ring of a bearing 62 that pivotallysupports the above output shaft 512 is held by the internal peripheralsurface 61F of the bearing holding part 561E.

The pump body 520 includes, as shown in FIG. 29, a casing body 522 whichis fitted into the fitting cavity 563 which is formed at the front sideof the case 511 of the electric motor 510, a cylinder part 523 which ispress fitted in the casing body 522 and forms a cylinder chamber S, anda pump cover 524 which covers the casing body 522 from the front side.In this embodiment, a casing 531 of the vacuum pump 501 is formed byincluding the casing body 522, the cylinder part 523 and the pump cover524.

The casing body 522 uses, for example, metal materials such as aluminumwhose thermal conductivity is high, and as shown in FIG. 30, the shapeof the casing body 522, when viewed from front, is formed to asubstantially rectangular shape which is longer in the up-down directionwith the above-mentioned rotation center X1 as an approximate center. Acommunicating hole 22A, which communicates with the cylinder chamber Swhich the casing body 522 is provided with, is formed in the upper partof the casing body 522, and a vacuum absorbing nipple 530 is pressfitted to the communicating hole 22A. As shown in FIG. 29, the vacuumabsorbing nipple 530 is a direct pipe which extends upwards, and a pipeor a tube which supplies underpressure air from an external equipment(for example, a vacuum tank 507 (refer to FIG. 28)) is connected to oneend 30A of the vacuum absorbing nipple 530.

A bore 522B around a central axis X2 which extends in the front-reardirection is formed in the casing body 522, and a cylinder part 523which is formed to a cylindrical shape is press fitted into the bore522B. The central axis X2 is parallel with the rotation center X1 of theoutput shaft 512 of the above-mentioned electric motor 510, and as shownin FIG. 29, is offset to the upper left side relative to the rotationcenter X1. In this configuration, the central axis X2 is offset so thatthe outer peripheral surface 527B of the rotor 527 around the rotationcenter X1 is adjacent to the internal peripheral surface 523A of thecylinder part 523 that is formed around the central axis X2.

The cylinder part 523 is formed of metal material (in the presentembodiment, iron) which is the same as that of the rotor 527. With thisconfiguration, because the thermal expansion coefficients of thecylinder part 523 and the rotor 527 are the same, regardless oftemperature change of the cylinder part 523 and the rotor 527, thecontact of the outer peripheral surface 527B of the rotor 527 and theinternal peripheral surface 523A of the cylinder part 523 when the rotor527 is rotated can be prevented. The cylinder part 523 and the rotor 527may use different materials as long as they are metal materials thathave substantially the same thermal expansion coefficient.

Because the cylinder part 523 can be accommodated in the length range ofthe front-rear direction of the casing body 522 by press fitting thecylinder part 523 into the bore 522B which is formed in the casing body522, the cylinder part 523 is prevented from being protruded from thecasing body 522 and the casing body 522 can be downsized.

Furthermore, the casing body 522 is formed of material whose thermalconductivity is higher than that of the rotor 527. Thereby, since theheat that is generated when the rotor 527 and vanes 528 are rotationallydriven can be transmitted to the casing body 522 immediately, the heatfrom the casing body 522 can be dissipated sufficiently.

An opening 523B which is coupled with the communicating hole 22A of theabove described casing body 522 and the cylinder chamber S is formed atthe cylinder part 523, and the air passing through the vacuum absorbingnipple 530 is supplied to the cylinder chamber S through thecommunicating hole 22A and the opening 523B. Therefore, in thisembodiment, an intake path 32 is formed by including the vacuumabsorbing nipple 530, the communicating hole 22A of the casing body 522and the opening 523B of the cylinder part 523. At the lower part of thecasing body 522 and the cylinder part 523, discharging ports 522C and523C, which penetrate the casing body 522 and the cylinder part 523 andwhere the air compressed in the cylinder chamber S is exhausted, areprovided.

Side plates 525 and 526 which block the openings of the cylinder chamberS, respectively, are disposed at the rear end and the front end of thecylinder part 523. The diameter of the side plates 525 and 526 is set tobe larger than the inside diameter of the internal peripheral surface523A of the cylinder part 523. The side plates 525 and 526 are pressedagainst the front end and the rear end of the cylinder part 523,respectively, by being biased by gaskets 525A and 526A. Thereby, thesealed cylinder chamber S is formed inside the cylinder part 523 exceptthe opening 523B which is coupled to the vacuum absorbing nipple 530 andthe discharging ports 523C and 522C.

In the cylinder chamber S, the rotor 527 is disposed. The rotor 527 hasa cylindrical column shape which extends along the rotation center X1 ofthe electric motor 510, and has an axial bore 527A through which theoutput shaft 512 which is a driving shaft of the pump body 520 isinserted. Meanwhile, at positions away from the axial bore 527A in theradical direction, a plurality of guide grooves 527C are provided aroundthe axial bore 527A by being spaced in the peripheral direction with anequal angular interval. A spline hole, which is engaged with the splineshaft that is provided at the front end part 512A of the output shaft512, is formed at the above axial bore 527A, and the rotor 527 and theoutput shaft 512 is adapted to be spline connected.

The length in the front-rear direction of the rotor 527 is set to besubstantially equal to the length of the cylinder chamber S of thecylinder part 523, namely, the distance between the mutually opposedinside surfaces of the above-mentioned two pieces of side plates 525 and526, and the space between the rotor 527 and the side plates 525 and 526are substantially blocked.

The outer diameter of the rotor 527 is set so that, as shown in FIG. 30,the outer peripheral surface 527B of the rotor 527 keeps a minuteclearance from a part among the internal peripheral surface 523A of thecylinder part 523 that is located at the lower right side. Thereby, asshown in FIG. 30, a space of a crescent shape is formed between theouter peripheral surface 527B of the rotor 527 and the internalperipheral surface 523A of the cylinder part 523.

The rotor 527 is provided with a plurality of (in this example, fivepieces) vanes 528 which partition the crescent space. The vane 528 isformed into a board shape, and the length in the front-rear direction isset to be substantially equal to the distance between the mutuallyopposed inside surfaces of the two pieces of side plates 525 and 526,like the rotor 527. These vanes 528 are disposed to be extendable fromthe guide grooves 527C which the rotor 527 is provided with. The vanes528 are protruded outwards along the guide grooves 527C by a centrifugalforce with the rotation of the rotor 527 so that the front ends of thevanes 528 abut with the internal peripheral surface 523A of the cylinderpart 523. Thereby, the above-mentioned crescent space is partitionedinto 5 compression chambers P surrounded by two pieces of mutuallyadjacent vanes 528 and 528, the outer peripheral surface 527B of therotor 527 and the internal peripheral surface 523A of the cylinder part523. These compression chambers P rotates in the same direction with therotation of the arrow R direction of the rotor 527 with the rotation ofthe output shaft 512, and the capacity of each of these compressionchambers P becomes bigger at positions near the opening 523B, andbecomes smaller at positions near the discharging port 23C. That is,with the rotation of the rotor 527 and the vanes 528, the air taken inone compression chamber P from the opening 523B rotates and iscompressed with the rotation of the rotor 527, and is discharged fromthe exhausting port 23C.

In this configuration, the cylinder part 523 is formed in the casingbody 522, as shown in FIG. 29, by offsetting the central axis X2 of thecylinder part 523 to the upper left side relative to the rotation centerX1. Therefore, in the casing body 522, a big space in the directionopposite to that the cylinder part 523 is offset can be secured, and theexpansion chamber 533 which communicates with the discharging ports 523Cand 522C is formed in this space along the peripheral part of thecylinder part 523.

The expansion chamber 533 is formed as a big closed space along theperipheral part of the cylinder part 523 from a position below thecylinder part 523 to a position above the output shaft 512, andcommunicates with the exhausting port 524A which is formed in the pumpcover 524. After the compressed air which flows into the expansionchamber 533 is expanded and scattered in the expansion chamber 533, theair hits the wall of the expansion chamber 533 and is reflecteddiffusely. Thereby, since the sound energy of the compressed air isattenuated, the noise and the vibration in the air-exhausting can bereduced. In the embodiment, an exhausting path 537 is formed byincluding the discharging ports 522C and 523C, which are formed in thecasing body 522 and the cylinder part 523, respectively, the expansionchamber 533 and the exhausting port 524A.

In this embodiment, by arranging the cylinder part 523 to be offset fromthe rotation center X1 of the rotor 527, a big space at the peripheralpart of the cylinder part 523 at the side of the above mentionedrotation center X1 can be ensured in the casing body 522. Therefore,because the expansion chamber 533 can be integrally formed in the casingbody 522 by forming the big expansion chamber 533 in this space, it isnot necessary to provide the expansion chamber 533 outside the casingbody 522, the casing body 522 can be downsized and thus the vacuum pump501 can be downsized.

The pump cover 524 is arranged to the front side plate 526 via a sealingring 526A, and is fixed to the casing body 522 with a bolt 66. On thefront of the casing body 522, as shown in FIG. 29, a sealing groove 522Dis formed by surrounding the cylinder part 523 and the expansion chamber533, and an annular sealing member 67 is arranged to the sealing groove522D. The exhausting port 524A is provided in the pump cover 524 at aposition corresponding to the expansion chamber 533. The exhausting port524A is intended to exhaust the air which flows into the expansionchamber 533 to the outside of the device (the outside of the vacuum pump501), and a check valve 529 for preventing the countercurrent of airfrom the outside of the device into the pump is attached to theexhausting port 524A.

As mentioned above, the vacuum pump 501 is formed by coupling theelectric motor 510 and the pump body 520, and the rotor 527 connected tothe output shaft 512 of the electric motor 510 and the vanes 528 slidein the cylinder part 523 of the pump body 520. Therefore, it isimportant to assemble the pump body 520 in accordance with the rotationcenter X1 of the output shaft 512 of the electric motor 510.

Therefore, in this embodiment, the fitting cavity 563, which is centeredon the rotation center X1 of the output shaft 512, is formed at one endof the case 511 of the electric motor 510. On the other hand, on theback of the casing body 522, as shown in FIG. 29, a cylindrical fittingpart 522F is integrally formed to be protruded backwards around thecylinder chamber S. The fitting part 522F is formed concentrically withthe rotation center X1 of the output shaft 512 of the electric motor510, and is formed so that the outer edge of the fitting part 522F isengaged with the fitting cavity 563 of the electric motor 510 in apillbox manner.

Therefore, with this configuration, only by fitting the fitting part522F of the casing body 522 into the fitting cavity 563 of the electricmotor 510, the central locations can be easily put together and theassembly of the electric motor 510 and the pump body 520 can be easilyperformed. Further, on the back of the casing body 522, a sealing groove522E is formed around the fitting part 522F, and a circular sealingmember 535 is arranged to the sealing groove 522E.

In the small vacuum pump used in the brake device of an automobile,usually, a small lightweight rotor is used, and in order to assemble thepump efficiently, the rotor is not fixed at all relative to the outputshaft and is provided to be movable in the axial direction of the outputshaft. Additionally, because the rotor is cantilever supported at thefront end of the output shaft of the electric motor, when the rotor isrotated, it is very likely that the rotor is protruded to the front endside of the output shaft with the rotation. Therefore, in theconventional configuration, in the operation of the vacuum pump, sincethe rotor contacts with the front side plate, the rotor and the sideplate are damaged due to the abrasion, and there is a problem that thedurability of the vacuum pump is decreased. In order to solve thisproblem, this configuration has a feature in the coupling structure ofthe rotor 527 and the output shaft 512.

FIG. 31 is an exploded perspective view which shows the couplingstructure of the rotor 527 and the output shaft 512.

The rotor 527, as described above, is spline connected with the outputshaft 512, and since the rotor 527 is locked to the output shaft 512with a push nut 570, the movement of the rotor 527 to the front end sideof the output shaft 512 is regulated.

In particular, a spline bore 527D is formed in a part of the axial bore527A of the rotor 527, as shown in FIG. 31, and by engaging the splinepart 12B formed in the front end part 512A of the output shaft 512 withthe spline bore 527D, the rotor 527 and the output shaft 512 are splineconnected. Thus, after the rotor 527 and the output shaft 512 are splineconnected, the rotor 527 is movable axially on the spline part 512B.

A columnar recess 527F whose diameter is larger than the axial bore 527Ais formed around the axial bore 527A at the front end surface 27E of therotor 527. A locking part 512C and a diameter-reduced part 512D of theoutput shaft 512 which is inserted into the axial bore 527A extend inthe recess 527F, and the push nut 570 is locked in the recess 527F tothe locking part 512C of the output shaft 512.

The push nut 570, as shown in FIG. 32, includes a ring-like andboard-like flange part 571, and a plurality of (five) claw parts 572which are formed to be protruded from the inner peripheral part of theflange part 571 to the central direction in a top view. These five clawparts 572 are substantially equally arranged at the inner peripheralpart of the flange part 571, and are formed so that the diameter D2 ofthe locking part 512C of the output shaft 512 is slightly bigger thanthe inside diameter D1 of an opening 573 formed at the front ends 572Aof these claw parts 572.

Thereby, when the push nut 570 is fitted to the locking part 512C, eachof the claw parts 572 transforms, and the claw parts 572 and the outerperipheral surface of the locking part 512C are locked with a restoringforce of these claw parts 572. Because the flange part 571 of the pushnut 570 abuts against the bottom surface (end surface) 27F1 (FIG. 31) ofthe recess 527F, the movement of the rotor 527 to the front end side ofthe output shaft 512 is regulated.

Therefore, with a simple configuration that the push nut 570 is attachedto the output shaft 512, since it can be prevented that the rotor 527and the front side plate 526 contact, the abrasion of the rotor 527 andthe side plate 526 is inhibited and the durability of the vacuum pump501 can be improved. Furthermore, because the push nut 570 is easilyattached to the locking part 512C of the output shaft 512 in comparisonwith other fastening means such as bolts, the movement of the rotor 527to the front end part 512A of the output shaft 512 can be prevented withan easy and short-time operation.

If the rotor 527 is only fixed to the output shaft 512, of course it ispossible to use the fastening means such as bolts. However, highefficiency and time-shortening in the assembly of pumps are required,for example, for the small vacuum pump 501 of the present embodiment,and when the rotor 527 is fixed to the output shaft 512, it is necessaryto perform operations of positioning and fixing the rotor 527 in a shorttime (for example, around ten seconds).

Then, with reference to FIGS. 33A to 33C, assembling procedures of therotor 527 is described.

In FIGS. 33A to 33C, the descriptions of the case 511 of the electricmotor 510 and the casing body 522 are omitted.

At first, as shown in FIG. 33A, the rotor 527 is inserted into theoutput shaft 512, and the spline part 512B of the output shaft 512 andthe spline bore 527D of the rotor 527 are spline connected. In thiscase, because the length of the rotor 527 is set to be substantiallyequal to the length of the cylinder chamber S (FIG. 29), the rotor isinserted until the rear end surface 27G of the rotor 527 abuts againstthe back side plate 525, and the front end surface 27E of the rotor 527and the opening of the cylinder chamber S becomes substantially flush.

Then, the push nut 570 is locked to the locking part 512C of the outputshaft 512. When the rotor 527 is inserted into the output shaft 512until the rotor 527 abuts against the side plate 525, as shown in FIG.33B, the locking part 512C of the output shaft 512 is extended in therecess 527F formed in the rotor 527.

In the embodiment, as shown in FIG. 32, the output shaft 512 includesthe locking part 512C and the diameter-reduced part 521D whose diameteris smaller than that of the locking part 512C, and the diameter D1 ofthe diameter-reduced part 512D is formed to be substantially equal tothe inside diameter D1 of the opening 573 surrounded by the front ends572A of the plurality of claw parts 572 of the push nut 570. Therefore,by fitting the push nut 570 to the diameter-reduced part 512D and makingthe push nut 570 to move along the diameter-reduced part 512D, the pushnut 570 can be guided to the locking part 512C without being inclinedrelative to the output shaft 512. Furthermore, a chamfering processingis given to the corner 512E of the diameter-reduced part 512D, and thepush nut 570 can be easily fitted to the diameter-reduced part 512D.

Then, as shown in FIG. 33C, by pressing the push nut 570 until the pushnut 570 abuts against the bottom surface 27F1 of the recess 527F of therotor 527, the push nut 570 is locked to the locking part 512C of theoutput shaft 512.

In this case, the push nut 570 is attached to the output shaft 512 byusing an exclusive jig (not shown in the figure) whose pressing load canbe measured. By pressing down until the pressing load F exceeds apredetermined threshold (for example, 100N), the rotor 527 is positionedby being held by the back side plate 525 and the push nut 570.Therefore, the positioning of the rotor 527 relative to the output shaft512 can be easily performed with an easy operation of inserting therotor 527 into the output shaft 512 until the rotor 527 abuts againstthe side plate 525, by pressing the push nut 570 against the bottomsurface 27F1 of the recess 527F of the rotor 527 until a predeterminedreference value is exceeded, it can be easily determined whether thepositioning of the rotor 527 is completed based on whether the referencevalue is exceeded, and the assembly of the pump can be performed in ashort time even if there is no experienced person.

In this situation, because the rotor 527 is positioned by being incontact with the back side plate 525, in the initial operation of thevacuum pump 501, since the rotor 527 and the side plate 525 slide,initial abrasion is produced in the rotor 527 and the side plate 525 by.However, at the time of the operation of the vacuum pump 501, because aforce that presses the rotor 527 against the push nut 570 is produced,the contact of the rotor 527 and the side plate 525 is prevented, andthe abrasion of the rotor 527 and the side plate 525 is prevented afterthat.

As described above, according to the present embodiment, the casing 531attached to the electric motor 510, the hollow cylinder chamber S whichis formed in the casing 531 and has the openings at the two ends of thecasing 531, the rotor 527 which is provided to be movable in the axialdirection relative to the output shaft 512 of the electric motor 510 andwhich is rotationally driven in the cylinder chamber S with the outputshaft 512, and the pair of side plates 525 and 526 which block theopenings of the rotor 527 are included, and the push nut 570 whichregulates the movement of the rotor 527 to the front end part 512A ofthe output shaft 512 is provided to the output shaft 512. Therefore, bypreventing the contact of the rotor 527 and the front side plate 526with a simple configuration, the abrasion of the rotor 527 and the sideplate 526 is inhibited and the durability of the vacuum pump 501 can beimproved. Furthermore, because the push nut 570 is easily attached tothe output shaft 512 in comparison with other fastening means such asbolts, the movement of the rotor 527 to the front end part 512A of theoutput shaft 512 can be prevented with an easy and short-time operation.

According to the present embodiment, the rotor 527 is inserted into theoutput shaft 512 until the rotor 527 abuts against the back side plate525 located at the side of the electric motor, and in this state, bypressing the push nut 570 against the end surface of the rotor 527 untila predetermined reference value is exceeded, the push nut 570 is lockedto the output shaft 512. With an easy operation of inserting the rotor527 into the output shaft 512 until the rotor 527 abuts against the sideplate 525, the positioning of the rotor 527 relative to the output shaft512 can be performed easily. By pressing the push nut 570 against theend surface of the rotor 527 until a predetermined reference value isexceeded, it can be easily determined whether the positioning of therotor 527 is completed based on whether the reference value is exceeded,and the assembly of the pump can be performed in a short time even ifthere is no experienced person.

In this case, because the rotor 527 is positioned by being in contactwith the back side plate 525, in the initial operation of the vacuumpump 501, since the rotor 527 and the side plate 525 slide, initialabrasion is produced in the rotor 527 and the side plate 525. However,at the time of the operation of the vacuum pump 501, because a forcethat presses the rotor 527 against the push nut 570 is produced, thecontact of the rotor 527 and the side plate 525 is prevented, and theabrasion of the rotor 527 and the side plate 525 is prevented afterthat.

According to the embodiment, the output shaft 512 includes the lockingpart 512C, to which the plurality of claw parts 572 of the push nut 570are locked, at the front end part 512A, and the diameter-reduced part521D whose diameter is smaller than that of the locking part 512C, andthe diameter of the diameter-reduced part 512D is formed to besubstantially equal to the inside diameter of the opening 573 surroundedby the front ends 572A of the plurality of claw parts 572 of the pushnut 570. Therefore, by making the push nut 570 to move along thediameter-reduced part 512D, the push nut 570 can be guided to thelocking part 512C without being inclined relative to the output shaft512. Therefore, by pressing the push nut 570 guided to the locking part512C against the rotor 527, the likelihood of failing to install thepush nut 570 due to the inclination of the push nut 570 can be reduced,and while the operation procedure is simplified, the operation time canbe shortened.

According to the present embodiment, the recess 527F is formed at thefront end surface 27E of the rotor 527 around the axial bore 527A wherethe output shaft 512 is inserted, and the push nut 570 is locked to thelocking part 512C of the output shaft 512 in the recess 527F. Therefore,without making the front end part 512A of the output shaft 512 to beprotruded from the front end surface 27E of the rotor 527, the push nut570 can be locked to the output shaft 512 and the configuration of thevacuum pump 501 can be simplified.

The preferred embodiments for performing the present invention aredescribed as above, but the present invention is not limited to thepreviously described embodiments, and various modifications and changesare possible based on the technical thought of the present invention.

INDUSTRIAL APPLICABILITY

The present invention can be applied to a vacuum pump (compressingdevice) that includes rotary compressing elements in a casing. Inparticular, the present invention can be applied to a vacuum pump whichhas a rotor that is attached to a rotary shaft of a vane-type drivingmachine. For example, the present invention can be applied to a vacuumpump which is carried in an engine room of an automobile, and is used toproduce a vacuum to operate a brake boosting device.

REFERENCE SIGNS LIST

-   80, 101, 200, 201, 202, 301, 401, 501 vacuum pump (compressing    device)-   506 brake booster (brake boosting device)-   507 vacuum tank-   509 brake pipe-   10, 110, 310, 410, 510 electric motor (driving machine)-   11, 211, 411, 511 case-   211A space (resonance chamber or intake side expansion chamber)-   12, 412, 512 output shaft (rotary shaft)-   20, 120, 220, 320, 420, 520 pump body-   22, 122, 222, 322, 422, 522 case body-   22A, 122A communicating hole-   22B, 122B bore-   22C, 122C exhausting port-   122F fitting part-   123, 223, 423, 523 cylinder part-   23 cylindrical liners-   23C exhausting port-   23C1 taper surface-   123B opening (communicating hole)-   224A, 424A exhausting port-   123C discharging port-   24, 84, 124, 224, 424 pump cover-   27, 127, 227, 327, 427, 527 rotor (rotary compressing element)-   28, 128, 228, 328, 428, 528 vanes (rotary compressing element)-   130, 230, 280, 430 vacuum absorbing nipple (inlet pipe)-   31, 131, 331 casing-   33, 133, 233 expansion chamber-   433 expansion chamber (other space whose pressure is above the    atmospheric pressure)-   233A first orifice-   234 resonance chamber-   235A orifice-   40, 237, 437 exhausting path-   238, 438 intake side expansion chamber-   40A inside course-   40B outside course-   40C turning part-   41 separating wall-   41A one end-   41 B the other end-   44A, 44B silence member-   163 fitting cavity-   160A1 part-   160C1 bore-   260, 460 case body-   261,461 cover body-   461A disk part (wall surface)-   470 space-   471 communicating hole-   472 exhausting port (communicating hole)-   264 second orifice-   265 desiccating agent-   268 communicating hole-   271 first communicating hole-   272 second communicating hole-   371, 375 groove-   381 labyrinth passage-   81 pilot bearing-   84A bearing holding hole-   570 push nut-   571 flange part-   572 claw part-   572A front end-   573 opening-   500 brake device-   F pressing load-   P compression chamber-   R arrow-   S cylinder chamber-   X1 rotation center-   X2 central axis

1. A vacuum pump comprising: rotary compressing elements in a casing,wherein the casing comprises a cylinder chamber in which the rotarycompressing elements slide, an expansion chamber which makes acompressed air exhausted from the cylinder chamber to be expanded, andan exhausting path which connects the cylinder chamber and the expansionchamber, and at least one turning part is provided in the exhaustingpath.
 2. The vacuum pump according to claim 1, wherein the exhaustingpath and the expansion chamber are adjacently provided at a peripheralpart of the cylinder chamber in the casing.
 3. The vacuum pump accordingto claim 1, wherein a silence member formed of porous material isarranged in the exhausting path.
 4. The vacuum pump according to claim1, wherein the casing comprises a cylindrical liner which forms thecylinder chamber, the cylindrical liner comprises an exhausting portwhich is connected to the exhausting path, a diameter of the exhaustingport at an inside of the cylinder chamber is larger than a diameter ofthe exhausting port at an outside of the cylinder chamber, and theexhausting port is formed to a taper shape whose diameter is reducedfrom the inside to the outside.
 5. The vacuum pump according to claim 1,wherein a rotary shaft which drives the rotary compressing elements iscomprised, and a front end part of the rotary shaft is supported with abearing which is provided in the casing.
 6. A vacuum pump comprising:rotary compressing elements in a casing, wherein the casing comprises: acasing body which is formed of material whose thermal conductivity ishigher than that of the rotary compressing elements, and a cylinder partwhich is press fitted in the casing body and in which the rotarycompressing elements slide.
 7. The vacuum pump according to claim 6,wherein the casing body and the cylinder part comprises a communicatinghole which communicates with the cylinder part by penetrating throughthe casing body and the cylinder part, and while an inlet pipe isprovided at the communicating hole, a front end of the inlet pipe isengaged with the communicating hole of the cylinder part.
 8. The vacuumpump according to claim 6, wherein the cylinder part is formed of amaterial which has a thermal expansion coefficient that is substantiallyequal to that of the rotary compressing elements.
 9. The vacuum pumpaccording to claim 6, wherein in the casing body, the cylinder part isarranged at a position that is offset from the rotation center of therotary compressing elements, and the expansion chamber that communicateswith the cylinder part is formed at the peripheral part of the cylinderpart at the side of the rotation center.